VULNERABILITY INDICATORS FOR UNITED STATES-MEXICO TRANSBOUNDARY WATERSHEDS PROJECT NUMBER: W-03-18 RICHARD D. WRIGHT, SAN DIEGO STATE UNIVERSITY JOSE LUIS CASTRO, EL COLEGIO DE LA FRONTERA NORTE ALFREDO GRANADOS OLIVAS, UNIVERSIDAD AUTÓNOMA DE CUIDAD JUÁREZ NARRATIVE SUMMARY There is a need for indicators to help quantify the degree of sustainability of United States-Mexican transboundary watersheds with respect to their environmental characteristics. Although the Tijuana River Watershed (TRW) is our primary test bed for indicator development, we cooperated closely with colleagues from New Mexico State University who conducted similar research in the Paso del Norte section of the Rio Grande/Rio Bravo Watershed. The TRW team also included researchers from El Colegio de la Frontera Norte, Tijuana, and the Universidad Autónoma de Cuidad Juárez. The project was accomplished in several phases beginning with a review and assessment of the literature on watershed vulnerability indicators. This was followed by the identification of experts and a two-day meeting of those experts who developed sets of indicator selection criteria and watershed vulnerability indicators. This workshop was held on October 23-24, 2003 at New Mexico State University under the leadership of Drs. Christopher Brown and Brian Hurd. The indicators developed by the experts panel were then evaluated in terms of their applicability to the Tijuana River Watershed by the research team at San Diego State University and El Colegio de la Frontera Norte. In evaluating possible indicators particular attention was given to data availability, especially that concerning water quantity, water quality, and water supply. Tests were conducted with a small set of vulnerability indicators in order to better understand the pros and cons of indicator development for cross-border drainage basins. 1 VULNERABILITY INDICATORS FOR UNITED STATES-MEXICO TRANSBOUNDARY WATERSHEDS PROJECT NUMBER: W-03-18 RICHARD D. WRIGHT, SAN DIEGO STATE UNIVERSITY JOSE LUIS CASTRO, EL COLEGIO DE LA FRONTERA NORTE ALFREDO GRANADOS OLIVAS, UNIVERSIDAD AUTÓNOMA DE CUIDAD JUAREZ INTRODUCTION The transboundary watersheds of the United States-Mexico border are being impacted by significant, and in some cases, overwhelming stresses (GNEB 2000; USEPA 2002). A prime example is the Tijuana River Watershed (TRW). This largely semi-arid drainage basin is the westernmost of a set of transboundary watersheds that help to define the character of the border region (Wright, Garfield, and Winckell 1995). The watershed comprises an area of about 1,750 square miles that lies astride the California-Baja California border, approximately one-third in the United States and two-thirds in Mexico. It is located in the San Diego-Tijuana region which has received the greatest impact from NAFTA-related growth in the form of increasing development in the industrial-economic zone along the border. This region, which has a population of over four million, is one of the most rapidly growing sections of the border. This growth and associated land use changes are responsible for numerous problems in the watershed, including a decline in the quality of surface and ground water, increased runoff from winter storms with accelerated erosion and flooding, alteration of natural habitats, reduction in the amount of green areas, and an increase in the number of plant and animal species that are threatened or endangered. With this project researchers attempt to create and evaluate a set of indicators of the vulnerability of transborder watersheds with respect to their hydrological characteristics. Although the TRW served as the primary testbed, investigators coordinated closely with colleagues from New Mexico State University (NMSU) who conducted similar research in the Paso del Norte (PDN) region of the Rio Grande/Rio Bravo Watershed. The project employed a variable spatial resolution that allowed characterization of the watershed as a whole and examine differences between the United States and Mexican sections of the watershed and variations among the 12 sub-basins that comprise the TRW. The involvement of Mexican researchers helped to insure that the results reflect a binational perspective with respect to data requirements and availability. Identification of data gaps needed for improved monitoring of watershed vulnerability was conducted along with an evaluation of the most effective geospatial technologies for meeting data needs (Wright and Dow 2003). RESEARCH OBJECTIVES A watershed vulnerability indicator is a measure of the condition or health of a drainage basin (USEPA 1997). Indicators evolve from the analysis of raw data using a geographic information 2 systems (GIS). They can be aggregated with other measures to create high-level indices that form the apex of the information pyramid (See Figure 1). Conditions are of two basic types: Those that represent the state of the system relative to a desired state and those that measure changes in the state of the system (Walker and Reuter 1996). An example of the former is the percent of impermeable surface in a watershed, whereas the percent of temporal change in the area of impermeable surface is an example of the latter. A watershed vulnerability indicator is a variable that provides information about the conditions of a watershed and its susceptibility to deterioration. The criteria for selecting environmental indictors fall into three categories: technical, practical, and programmatic (Intergovernmental Task Force on Monitoring Water Quality 1995). Technical considerations include measurability, sensitivity, resolution, validity and accuracy, reproducibility, representiveness, scope, and data comparability. Practical considerations are cost and difficulty factors. Programmatic considerations includes relevance, program coverage, and understandability. For the sake of simplicity, and in order not to get bogged down by working with a large number of sometimes conflicting criteria, researchers employed a reduced set of environmental indicators for the study of the Tijuana River Watershed (TRW). This reduced set, which derives from the Phoenix study, “What Matters in Greater Phoenix” (Morrison Institute for Public Policy 1999), includes the following criteria: Is the indicator measurable? Are the data available at regularly measured intervals? Is the indicator relevant? Is the indicator understandable? Will the indicator respond to changes in policy and law? In addition to the above, investigators added the following question that takes into account the international character of the watershed: Are the data spatially comparable across the U.S.-Mexican border? The principal purpose of this project was to examine the degree to which environmental vulnerability can be measured at different scales and resolution for the TRW. To accomplish this, researchers endeavored to apply indicators for the TRW as a whole; the United States versus the Mexican sections of the basin; urban vs. rural sections; and for the 12 sub-basins of the watershed. A secondary purpose was to evaluate the suitability of different geospatial technologies for identifying and monitoring vulnerability indicators at different scales, resolution and locations. RESEARCH METHODOLOGY/APPROACHES Vulnerability Indicators Selection Process An important outcome of the Expert Panel Workshop held at New Mexico State on October 23-242003 was the development of a vulnerability indicators chart focusing on U.S.-Mexico border watersheds (See Table 1). Also, as a result of a presentation by William Kepner on the Automated Geospatial Watershed Assessment (AGWA) tool at the expert workshop, it was decided to hold a training workshop on the characteristics and applications of AGWA software for assessing the vulnerability of cross-border watersheds in the U.S.-Mexico border region. This workshop was conducted at San Diego State University on June 21-22, 2004 by Dr. Darius Semmens, U.S. EPA National Exposure Research Laboratory, Las Vegas. Twelve individuals from San Diego State 3 University, El Colegio de la Frontera Norte (COLEF) and Universidad Autónoma de Cuidad Juárez participated in the workshop. With the recommendations of the aforementioned expert panel in mind, the project researchers at SDSU and COLEF developed an initial set of vulnerability sources and related indicators for the TRW (See Table 2). For each indicator investigators assessed data availability at four different levels: the TRW as a whole, the U.S. and Mexican sections of the TRW, the 12 sub-basins of the TRW, and the urban areas of the watershed (Tijuana, Tecate, and San Ysidro). From this table researchers selected a set of four watershed vulnerability topics for more detailed analysis. They are described in the following section. Vulnerability Topics Of the many water-related problems in the Tijuana River Watershed, those concerned with flooding, water pollution, erosion/sedimentation, and potable water supply and population expansion are the most pressing. While many areas of the watershed are subject to temporary inundation due to intense precipitation events, the likelihood of flooding has increased as a result of several factors. They are urbanization, stream channelization, vegetation modification/removal, and sand mining. The aerial expansion of Tijuana, Tecate, and San Ysidro, in particular, has increased the percentage of impermeable surface, especially in the lower section of the watershed. Stream channelization in the City of Tijuana has eliminated severe flooding along the main stream and encouraged economic development in the Zona Rio section. However, channelization has had negative effects such as decreased groundwater recharge and increased flooding downstream in the U.S. section of the lower valley. Vegetation removal, particularly on steep hillsides, has led to more rapid runoff. Sand mining in the Valle las Palmas and other more accessible stream valleys has decreased the groundwater storage capacity of the shallow aquifers and allowed surface water to flow downstream more quickly. The result of the above is that after a storm event, streams are characterized by higher volume peak discharge, increased total runoff volume, steeper recession of discharge, and lower base flow. Flood vulnerability indicators include precipitation (quantity and frequency), stream flow, hypsography, impervious surface area, quality and quantity of vegetation cover, and extent of material extraction. The downstream effects of point and non-point source pollution in the TRW are severe. Beaches near the mouth of the river are among the most polluted water in California (Gersberg et al. 2000). Factors leading to polluted water in the TRW are runoff from different land uses, industrial/toxic discharges, inadequate sewage treatment, and poor natural filtering of water. Storm water runoff from industrial, agricultural, and residential land uses is a major contributor to water pollution in the lower watershed. Unregulated industrial discharges contribute to poor water quality as well. Although a program of industrial pre-treatment has been instituted in Tijuana, much needs to be done to expand it to the entire urban area. Many areas of Tijuana and Tecate are not connected to sewage treatment facilities and/or are subject to sewage overflows during precipitation events. Finally, pollution of water from point and non-point sources in the TRW is exacerbated by poor natural filtering of water owing to stream channelization and sand mining. Water quality model inputs include many variables, including precipitation, stream flow, hypsography, land use, impervious surfaces, number and severity of spills, percent of area not served by a municipal sewage system, quality and quantity of vegetation cover, extent of riparian vegetation, extent of material extraction, and industrial pre-treatment requirements. 4 Intense precipitation events have contributed to severe erosion of moderate to steeply sloping terrain and the resultant deposition of sediment on relatively flat areas. Sediment deposition has been extremely heavy in the Tijuana River National Estuarine Research Reserve, resulting in the loss of as much as eight acres of coastal marsh in one recent storm. Erosion has been especially severe on the steeply sloping sides of the mesas in Tijuana. These slopes, comprised of loosely consolidated sedimentary rocks, have become more unstable as a result of vegetation removal owing to urban development on steep slopes. Grading in the vicinity of the U.S.-Mexican border fence in order to accommodate the mandate of the U.S. Border Patrol for border security has exacerbated erosion in the lower valley on the U.S. side of the border. Wildfires, such as those that occurred in different parts of the watershed in the fall of 2003, also contribute to erosion and sedimentation through the destruction of vegetation cover. Possible erosion/sedimentation vulnerability indicators considered in this project include precipitation amount and intensity, slope steepness, vegetation cover, soil characteristics, surface impermeability, and grading in the vicinity of the border fence. Relevant models investigated are the Revised Universal Soil Loss Equation (USDA 1997), which estimates erosion in tons per acre per year based on the physical characteristics of the environment, and the Erosion Hazard Rating System (CDPR 1991), which rates the erosive potential of slopes based on physical characteristics of the environment. The lower part of the TRW, wherein more than 95 percent of its population resides, is a water deficit area. Tijuana and Tecate rely on imported Colorado River water for more than 95 percent of their supply, whereas the comparable figure for the urban areas of San Diego County is 85 percent or more, depending upon precipitation and the replenishment of local reservoirs. Upstream of the urban areas, residents are totally dependent on groundwater for household and agricultural uses. Rapid population growth in Tijuana and Tecate is placing increasing stress on available supplies. Local supplies, already limited in quantity, are being degraded as a result of pollution of surface water and groundwater aquifers. Additionally, a dilapidated water delivery infrastructure means that much water is lost due to leaks in the system. Another consequence of rapid population growth is that water agencies are unable to expand the infrastructure fast enough to meet industrial and residential demand. In reviewing indicators of potable water supply vulnerability those that seemed most promising are rate of population growth, urban area and population without access to piped water, reliance on imported water, contamination levels in groundwater, contamination levels in surface water, and policies regarding water use. Impervious Surface Modeling In recent years, impervious surfaces have become recognized as a key factor in watershed planning (Brabec et al. 2002). In many instances, impervious surfaces can act as an indicator of watershed health, and may be used to estimate current water quality conditions. When less than 10% of a watershed is considered to be impervious, the impacts on water quality are slight, and water quality remains protected. Imperviousness between 10% and 25%, generally indicates that water quality is impacted to a moderate degree. As the imperviousness of a watershed increases to 25% or greater, water quality is considered impacted (Schueler 1994). Early efforts to calculate the imperviousness of different land uses relied primarily on four methods. These included: identifying impervious areas using aerial photography and a planimeter to measure 5 each area; using grid overlays with aerial photos to find the number of intersections that overlaid different land uses or impervious features; using supervised classification of remotely sensed imagery; and equating the percentage of urbanization in a region with the percentage of surface imperviousness (Brabec et al. 2002). More recently, research has focused on using new technologies to accurately determine impervious surfaces. According to Yang (2003), considerable work has been done in determining impervious surfaces using multiple regression (Forster 1980; Ridd 1995), spectral un-mixing (Ji and Jensen 1999; Ward et al. 2000), sub-pixel impervious surface mapping using artificial neural network and ERDAS Imagine sub-pixel classifier (Wang et al. 2000; Flanagan and Civco 2001), classification trees (Smith et al. 2003), and the integration of remote sensing with GIS (Prisloe et al. 2001). A method recommended by Civco and Hurd (2004) uses percent impervious surface coefficients as a function of land cover type to estimate imperviousness. Another option is to perform sub-pixel percent impervious surface modeling using Landsat TM and ETM+ data. This method uses ERDAS Imagine Sub-Pixel Classifier and performs a supervised classification. Essentially, it identifies and removes unwanted spectral materials that contribute to the background of the pixels, and then compares the remaining spectrum to the signature of the material of interest. An alternative method that extracts sub-pixel imperviousness using a regression tree algorithm, Landsat-7 ETM+, and two high spatial resolution images has recently been developed as a means of providing higher accuracy in impervious surface measurement. This method involves the selection of an algorithm and training data for each study area in order to represent the spectral and spatial variability of impervious surfaces. A predictive variable is selected and the regression tree modeling is initiated. A final regression tree model is selected and the results are mapped (Yang 2003). Another resource and possible method for determining impervious surfaces is the Impervious Surface Analysis Tool (ISAT). Developed by the National Oceanic and Atmospheric Administration (NOAA) Coastal Services Center and the University of Connecticut’s Nonpoint Education for Municipal Officials (NEMO), ISAT is a GIS software extension that uses land cover to estimate surface imperviousness. This extension was developed for use in ArcView and uses basins, municipal boundaries, open space lands, and satellite-derived land use and land cover (LULC). The derived LULC is than used to determine specified impervious surface coefficients. These coefficients represent the percentage of imperviousness for a land cover class and, although originally developed for Connecticut, can be applied and modified for use in other geographic regions. The model has the capability to estimate the overall imperviousness of a watershed as well as produce watershed maps using these surface coefficients (Prisloe et al. 2000). Chabaeva et al. (2004) noted that although there are many different techniques that can be used to measure or estimate surface imperviousness, most are fairly time consuming as well as costly. For example, although heads up digitizing of remotely sensed images, sub-pixel classification, artificial neural networks, and classification and regression trees are more accurate than other methods, they require moderate to high resolution images as well as a high degree of expertise in terms of processing and analysis. In this research we employed the Impervious Surface Analysis Tool (ISAT), a GIS extension developed for ArcView. Prior to running ISAT the land use and vegetation layer were merged to create a land cover data set. The original TRW vegetation and land use classes were reclassified to conform to the 18 land use classes provided in ISAT. Default impervious surface coefficients (low, 6 medium, high) were then assigned to these new classes. The coefficients were originally developed based on impervious surface data for the State of Connecticut, but can be modified for use in other geographic regions. The ISAT model was run using the following inputs: Analysis Theme: Watershed sub-basins (polygon shapefile or coverage). This defines the areas over which impervious surface estimates will be calculated Land Cover Grid: A combination of the land use and vegetation layer (in grid format) Population Density Theme: Population density for each of the sub-basins. The imperviousness of a single land cover class is affected by population density. Depending upon the population density (< 250 = low, 250 – 2,500 = medium, and > 2,500 = high), different coefficients will be applied Impervious surface coefficients are applied to determine the total as well as the percentage of impervious surface area within specified polygons. After running the model, an imperviousness layer was generated which listed by sub-basin the percentage of imperviousness per hectare (See Table 3). Several assumptions were made in running ISAT: Stream quality is a function of the percentage of impervious surface area Each watershed operates independently of upstream watersheds Watershed characteristics such as soils, topography, and stream density are not considered No distinction is made between total and effective impervious area The spatial distribution of impervious surface and its proximity to drainage systems is ignored ISAT uses Spatial Analyst to overlay polygon data (watershed boundaries) on land cover data to calculate the area of each land cover category within each polygon Avenue scripts are then used to apply impervious surface coefficients (ISi) to calculate the impervious area percentage for each polygon (ISW), by using the following equation: n ISW = ∑ Areai * ISi _i = 1 _________________ Total Area Water Quality Modeling Using ISAT, the potential impact to water quality within a watershed is based upon the estimated percentage of surface imperviousness. Areas within a watershed that have <10% impervious surfaces are considered protected; areas with 10% to 25% impervious surfaces are considered degraded; and those areas that have 25% and greater imperviousness are impacted. Although ISAT uses percent imperviousness as a measure of water quality, other studies have relied on storm water runoff to measure water quality within a watershed. For example, in a study by Englert (1997), impacts to water quality were associated with storm events, where water pollution was considered to be a result of waste water discharge and storm water runoff. When determining 7 storm runoff quantity, the percent imperviousness of land cover is the single most important factor. In addition, nonpoint source pollution such as organic chemicals, metals, nutrients, and pathogens are also commonly associated with storm water runoff. In the Englert study, land use classifications were developed for each of the 12 sub-basins. The percent of impervious surfaces was then determined for each of these land use types in order to provide an estimate of runoff coefficients. These coefficients are useful since they are a measure of a watershed's response to rainfall events. The average monthly rainfall was used to indicate runoff; only rainfall events with a minimum of 0.10 inches were used (these are considered large enough to generate significant runoff volumes). Storm runoff was then calculated based on the predicted rainfall for each land use classification. The appropriate runoff coefficients were then applied in order to calculate storm runoff. In addition to rainfall and runoff, pollutant loadings and concentrations (non-point source) were determined. These factors were used as water quality parameters for the study. Erosion/Sedimentation As mentioned previously, erosion and associated sedimentation are serious problems in the TRW. It was determined that this indicator could be quantified through the use of AGWA (Automated Geospatial Watershed Assessment). AGWA, a tool developed by the Environmental Protection Agency and the Department of Agriculture, incorporates two watershed models: KINEROS for small (<=100 km2) watersheds and SWAT for large (>100 km2). Since the Tijuana River Watershed is considered a large watershed, the SWAT (Soil and Water Assessment Tool) model is most appropriate for implementation. The outputs for this model include precipitation, evapotranspiration (ET), percolation, surface runoff, transmission loss, water yield, and sediment yield. These data can be used to evaluate various management scenarios that involve runoff and erosion. One of the major difficulties for implementing models in a transboundary watershed is identifying comparable datasets that can be used as input parameters (Wright and Winckell 1998; Wright et al. 2000). The AGWA model requires the following inputs: digital elevation model (DEM), land use/land cover, soils (STATSGO), streams, precipitation gauges, and gauging stations. In case of the Tijuana River Watershed, the major limitation is the lack of a continuous STATSGO soils dataset. On the U.S. side of the border, soils data are organized according to the STATSGO system, while soils data on the Mexican side are classed according to the FAO system. In order to run the model, an improvised soil layer was used. However, this did not produce accurate results. Another weakness of using this model in the Tijuana River Watershed results from the lack of precipitation gauges throughout the watershed. Since there are so few gauges, the precipitation surface is highly interpolated which decreases the accuracy of the final outputs. Water Supply The Tijuana River Watershed has a dynamic urban population, mostly concentrated on the Mexican part of its territory. This population has grown steadily at a 5% annual rate for the past 30 years and is clearly one of the major threats for the stability of the watershed. A measure that can provide insight on the vulnerability of the TRW is the volume of water available for each inhabitant. 8 The data available for the estimation of this indicator present differences when comparing the Mexican and U.S. portions of the watershed. In the former case, the information on water supply for the TRW is comparatively dispersed. In Baja California the agencies that manage the water at the local level, the Comisiones Estatales de Servicios Públicos (CESPs; in English the State Commissions of Public Services), carry their own statistics on water supply, including both surface and underground sources, as well as local and imported ones. Two other state agencies, the Comisión Estatal de Agua del Estado (CEA; State Water Commission) and the Comisión de Servicios de Agua del Estado (COSAE; State Commission of Water Services), provide information on the annual volumes transported by the Colorado River-Tijuana Aqueduct to the Tecate and Tijuana municipalities, as well as the underground sources inside the TRW. Finally, the Comisión Nacional del Agua (CAN; National Water Commission), is the main water agency at the federal level and provides information on annual surface and underground yields. Besides the dispersed sources, the data from these varied sources are not complete for comparison on a yearly basis. In order to assemble a comparable time series data set (Table 4), two considerations were made. The first was to eliminate the year 2004 from the data set. The second was the assumption of constant volumes of local underground water (the data from CNA identified the three aquifers in the TRW – Tijuana, Tecate, and Las Palmas – as in equilibrium). A large part of the U.S. portion of the TRW is not urbanized. The data on water availability and population are difficult to gather for this area. The urban areas represent a smaller part of the watershed, and their water services are provided by two of the San Diego County Water Authority‘s (SDCWA) member agencies: The City of San Diego and the Otay Water District. In order to estimate comparable indicators with the Mexican portion, total water supplied and population served were used for each agency for the years reported by SDCWA. The results are shown in Table 5. Table 5 compares the three indicators estimated for the 1999-2003 period. As observed, the areas in the U.S. portion of the TRW with regular public water service, present higher per capita volumes than those in the Mexican side. Even if one uses urban population to calculate the indicator in the second case (Table 4), the results do not vary notably. Another noticeable difference found between the two sides of the TRW is the growing availability of water on the U.S. communities. One conclusion here is that while the agencies serving the Mexican portion have kept the supply of water constant, they will certainly be forced to consider new alternatives as a result of population growth. Population Density Population density and change in density are useful indicators of the pressure placed on the environmental resources of a watershed. In the TRW, the highest densities are found in San Ysidro, Tijuana, and Tecate. Elsewhere, except for a few small population clusters in Nueva Colonia Hindu, Valle de las Palmas, Carmen Serdán, Vallecitos, Santa Verónica, Nejí, El Hongo, Potrero, Campo, and Pine Valley, population is highly dispersed. Density changes are greatest in the outskirts of Tijuana and Tecate where new homes are spreading rapidly over the rural landscape. Rosarito, Tijuana and Tecate – with Rosarito located outside of the watershed – are expanding toward each other and will eventually form a contiguous metropolis. Tijuana is also expanding to the southeast and is likely to connect with the community of Valle de las Palmas in the next decade. 9 Geospatial Technologies and Data Sources Geospatial technologies offer opportunities for identifying and monitoring watershed conditions in the U.S.-Mexican border region. This section summarizes the characteristics of geospatial technologies and their use for monitoring watershed conditions (Stow et al. 1998). A large suite of imagery types is available for monitoring watershed health indicators. Imagery varies in its spatial, spectral-radiometric, and temporal dimensions. When determining which type of imagery to utilize, there are some basic choices and trade-offs that must be made, including: aircraft vs. satellite imagery; analog vs. direct digital imagery; panchromatic vs. multispectral; spatial resolution vs. geographic extent; temporal resolution; and cost. Digital orthophotos are aerial photographs that are terrain-corrected and geo-referenced. Orthophotos are an important source of data for indicators requiring visual interpretation of highresolution imagery. Global Positioning Systems (GPS) facilitate the determination of locations in two- and threedimensional space. With GPS the user is able to determine the location of monitoring data and sensing instruments. A digital elevation model is a set of elevation values for a given geographical area. Digital elevation models are important for producing terrain-corrected imagery and for generating a variety of products such as watershed and stream boundaries. Additionally, they may be components of some environmental health indicators such as the percentage of impervious surface in the drainage basin. A geographic information system (GIS) is a computer-based technology that allows the user to convert geospatial data into information that can form the basis for decision-making. This technology allows indicators of environmental health and vulnerability to be studied within a spatial context. Cartographic visualization allows users to interpret, validate, and explore spatial data. Being able to graphically portray environmental health indicators allows environmental resource managers and researchers to effectively communicate information to others. PROBLEMS/ ISSUES ENCOUNTERED Investigators encountered a number of problems and issues in carrying out this project. The first concerned the necessity of identifying important environmental issues in different parts of the watershed. Fortunately, a project funded by the State of California to develop a binational vision for the TRW was carried out concurrently with this SCERP vulnerability indicators study. Stakeholders interviewed in the binational vision project identified a set of priority issues in different parts of the watershed. It was convenient to employ these priorities in the environmental indicators study. A second issue concerned the difficulty of finding indicators that meet the selection criteria. Of the six criteria previously discussed, those most problematic were: Is the indicator measurable? Are the data available at regularly measured intervals, and 10 Are the data spatially comparable across the U.S.-Mexican border? The final criterion is especially critical given that a requirement of this study is the integration of geospatial data for transboundary watersheds. Another issue of concern was the difficulty of settling on a small number of relevant indicators to best characterize the watershed’s environmental vulnerability. More than a hundred indicators have been identified in the literature. Narrowing the list to those that are most significant involves a selection process that represents a balance between indicators that are concept driven and those that are data driven. The final, and most difficult problem encountered in this project was the paucity of data for desired indicators. Data gaps were of several types. In some instances comparable data were not available for the U.S. and Mexican portions of the watershed. In other instances, there was a lack of data comparability between the urban and rural portions and the upstream and downstream sections. Finally, for all but a small number of measures, adequate data were not available at the sub-basin level for the twelve principal hydrologic subdivisions of the TRW. RESEARCH FINDINGS In conjunction with this research investigators experimented with indicators relevant to flooding, water quality, erosion/sedimentation, and water supply. Flooding As a partial indicator of flooding vulnerability an impervious surface layer was generated using the ISAT model. Table 3 shows that the Rio Tijuana sub-basin, with an imperviousness of 39.18%, is the only area of the 12 drainage basins that is severely impacted. Water Quality In addition to using ISAT to measure impermeability as a partial indicator of water quality, researchers compared the output from ISAT with that obtained by Englert in his storm water runoff study. The result of his study indicate that the sub-basins of Rio Tijuana and lower Cottonwood have the highest runoff percentage (11%), followed closely behind by Pine Valley and Upper Cottonwood (10%). The largest pollutant loadings and concentrations came from Rio Tijuana, which incidentally is also one of the smallest sub-basins. In addition, the border sub-basins of Upper Cottonwood and Pine Valley had the next highest pollutant levels. The results of the two studies are roughly comparable. Erosion/Sedimentation Our exploration on the use of AGWA for measuring transboundary watershed vulnerability indicators was only partly successful. A recent beta-version of AGWA (1.42 Beta) was released that allowed for FAO soils to be used as an input parameter; however, bugs within the software kept the model from running. After communicating with AGWA experts at the EPA, investigators made some progress, but not enough to actually produce meaningful output. However, work is being done on a new version of the AGWA tool, AGWA2, which may provide a more stable transboundary modeling environment. Project researchers plan to employ AGWA in the future, but more 11 calibration experimentation will be required before it can be applied successfully in the Tijuana River Watershed. Water Supply Tables 4 and 5 provide information to create an indicator on percentage of imported water in the TRW. Table 7 presents the corresponding figures. As this table shows, the TRW is highly dependent on imported water on both sides of the border. On the Mexican side, the data in Table 4 show some low figures of imported water during the first half of the 1990 decade, reflecting the effects of unusually large amounts of precipitation within the TRW during those years. However, on the whole, the Mexican portion of the watershed relies more on imported water for its needs, with the Colorado River water being the basic source. Since local sources are not reliable, dependence on the Colorado River water will increase. The varying implications of this situation reinforce the need for water agencies in this part of the TRW to emphasize their search for other alternatives beyond the Colorado River to meet their future requirements. The dependency indicator for the U.S. portion of the TRW also demonstrates high figures for the agencies in charge (Table 7). While the City of San Diego shows comparable figures to those of the Mexican portion, Otay Water District depends almost solely on imported water for its water uses. As critical as this condition may be, a major difference is that the supply for the U.S. water districts is guaranteed for at least the next 50 years through the agreements between SDCWA and the Metropolitan Water District (MWD), as well as the Imperial Irrigation District (IID). Population Density Increases in population density and urban expansion have led to environmental degradation, as represented by loss of natural vegetation, and is a problem in many parts of the watershed. The loss of vegetation results in fragmentation of habitat or the process of subdividing a continuous habitat into smaller, disconnected patches. Fragmentation, in turn, leads to a decrease in biological diversity. Changes in land use/land cover, particularly the conversion of natural cover to agricultural and urban uses, are seen throughout the watershed, but especially in the rapidly urbanizing Tecate-Tijuana section. Geospatial Technologies Geospatial technologies can be employed to provide timely, relevant, and reliable data that are comparable from one side of the border to the other. Many indicators cannot be identified and measured. However, those that might be identified through the use of geospatial technologies have not been fully utilized largely because of the high cost of imagery, software, and hardware and insufficient training in their use. CONCLUSIONS Project investigators reviewed a large number of watershed vulnerability indicators and their possible relevance to the measurement and monitoring of environmental conditions in the Tijuana River Watershed Indicators. Flooding, water quality, erosion/sedimentation, and water supply were 12 considered to be factors of major concern in the watershed. Indicators expressive of these factors are surface impermeability, potable water consumption, and population increase. Significant spatial variations in quality and availability of data greatly limit the number of useful indicators. Geospatial technologies used individually, in combination, or in combination with enumerated data and data from in-site sensors and networks can provide cost-effective data in support of transborder watershed health indicators. The Automated Geospatial Watershed Assessment tool has potential utility for estimating erosion/sedimentation indicators. RECOMMENDATIONS FOR FURTHER RESEARCH Indicator development is a promising approach for identifying and monitoring environmental conditions in transboundary watersheds in the U.S.-Mexican border region. However, to realize this potential, it is necessary that improvements be made in the quality and coverage of geospatial data. This will require additional research to determine the transboundary environmental health indicators for which geospatial technologies are most capable of being employed to generate relevant and timely indicator data. Additionally, exploration in the use of AGWA and other software tools for estimating watershed indicators relating to runoff and erosion would be beneficial. RESEARCH BENEFITS This project is an initial exploration of techniques for developing watershed vulnerability indicators for the United States-Mexico border region. It should assist in (a) prioritizing transborder watersheds according to their environmental deterioration and need of rehabilitation; (b) facilitating binational approaches in addressing water quality problems in shared water basins; (c) identifying watersheds that require improved water quality monitoring; (d) providing guidance in the selection of imagery and other geospatial technologies for identifying and monitoring watershed vulnerability; and (e) providing the basis for the development, implementation, and evaluation of policies for improving water resource conditions. ACKNOWLEDGEMENTS This work was sponsored by the Southwest Consortium for Environmental Research and Policy (SCERP) through a cooperative agreement with the U.S. Environmental Protection Agency. Contact SCERP for further information through www.scerp.org and scerp@mail.sdsu.edu. REFERENCES Blair, J. 2001. “An Evaluation of the EPA’s Border Environmental Indicators: Are They Measuring Up?” Project Number: CX827370-01-0. San Diego, CA: San Diego State University, Southwest Consortium for Environmental Research and Policy. Brabec, E., S. Schulte, and P. Richards. 2002. “Impervious surfaces and water quality: a review of current literature and its implications for watershed planning.” Journal of Planning Literature 16(4): 499-514. 13 Chabaeva, A., D. Civco, and S. Prisloe. 2004. “Development of a population density and land use based regression model to calculate the amount of imperviousness.” Proceedings of the 2004 ASPRS Annual Convention, Denver, CO. Civco, D. and J. Hurd. 2004. “Surface Water Quality and Impervious Surface Quantity: a Preliminary Study.” Storrs, CT: Center for Land use and Education and Research, University of Connecticut. Englert, P. 1997. “Characterizing urban storm water pollution in the Tijuana River Watershed.” Master’s thesis, Graduate School of Public Health, San Diego State University, San Diego, CA. Gersberg, R., R. Wright, J. Pitt, A. King, and H. Johnson. 2000. “Use of the BASINS Model to estimate Loading of Heavy Metals in the Binational Tijuana River Watershed,” Proceedings, Watershed 2000, July 2000, Vancouver, BC, Canada. Gleick, P. 1998. “An Overview of Water Resource Indicators: Problems and Promise.” Workshop on Water and Climate Change: Regions of Vulnerability, 29-30 January 1998, Boulder, CO. California Department of Parks and Recreation.1991. “Soil Conservation Guidelines/Standards for Off-Highway Vehicle Recreation Management.” Sacramento, CA. Hammond, A., A. Adriaanse, E. Rodenburg, D. Bryant, and R. Woodward. 1995. “Environmental Indicators: A Systematic Approach to Measuring and Reporting on Environmental Policy Performance in the Context of Sustainable Development.” Washington, DC: World Resources Institute. Morrison Institute for Public Policy. 1999. “What Matters in Greater Phoenix: Indicators of Our Qualify of Life.” Phoenix, AZ: Arizona State University. Prisloe, S., L. Giannotti, and W. Sleavin. 2000. “Determining Impervious Surfaces for Watershed Modeling Applications.” Proceedings of the 8th National Nonpoint Sources Monitoring Conference, Hartford, CT. Prisloe S., Y. Lei, and J. Hurd. 2001. “Interactive GIS-Based Impervious Surface Model.” ASPRS 2001 Annual Convention, St. Louis, MO. Schueler T. 1994. “The Importance of Imperviousness.” Watershed Protection Techniques 1(3): 100111. Schultz, M. 2001. “A Critique of EPA’s Index of Watershed Indicators.” Journal of Environmental Management. 62 (4): 429-442. Stow, D., J. Franklin, A. Hope, J. O’Leary, R. Wright, and P. Longmire. 1998. “An Assessment of the Potential of Geo-Spatial Technologies for Monitoring Shrubland Habitats in Southern California.” San Diego, CA: San Diego State University. Unpublished. 14 United States Department of Agriculture (USDA). 1997. “Predicting Soil Erosion by Water: A Guide to Conservation Planning with the Revised Universal Soil Loss Equation.” Washington, DC: Agricultural Research Service, USDA. United States Environmental Protection Agency (USEPA). 1997. “U.S.-Mexico border Environmental Indicators.” Washington. DC: USEPA. United States Environmental Protection Agency (USEPA). 1997. “The Index of Watershed Indicators.” Washington, DC: Office of Water, USEPA. United States Environmental Protection Agency (USEPA). 2003. “Border 2012.” Washington, DC: Office of Water, USEPA. University of Connecticut. 2005. “NEMO (Non-point Education for Municipal Officials).” University of Connecticut (cited 2005), http://nemo.uconn.edu. Walker, J. and D. Reuter. 1996. Indicators of Environmental Health. Collingwood, Victoria, Australia: CSIRO Publishing. Wright, R., N. Garfield, and A. Winckell. 1995. “Binational GIS Database Development for the Tijuana River Watershed.” Proceedings of URISA ’95, July 1995, San Antonio, TX. Wright, R. and A. Winckell. 1998. “Harmonizing Framework and Resource Data Across Political Boundaries.” Pp. 71-93 in GIS Solutions in Natural Resource Management, S. Morain, ed. Santa Fe, NM: OnWord Press. Wright, R., K. Conway, D. McArthur, and C. Tague, 2000. “Integrating GIS and Flood Hazard and Risk Modeling in a Cross-Border Data Poor Environment,” Proceedings of the Fourth International Conference on GIS and Environmental Modeling, September 2000, Banff, Alberta, Canada. Wright, R. and D. Dow. 2003. “The Potential of Geospatial Technologies for Monitoring Environmental Indicators in the United States-Mexico Border Region.” International Workshop on Remote Sensing, Elba Island, Italy. Yang, L., C. Huang, C. Homer, B. Wylie, and M. Coan. 2003. “An Approach for Mapping LargeArea Impervious Surface: Synergistic Use of Landsat-7 ETM+ and High Spatial Resolution Imagery.” Canadian Journal of Remote Sensing 29(2): 230-240. APPENDIX Report figures and tables 15 16 Table 1. Vulnerability Indicators Chart developed from October 23-24, 2003, Expert’s Panel Workshop, Revised 15 February, 2004 (continues on next four pages) Vulnerability Source Population growth Population water stress Consumptive use Ground water overdraft Degree of over-allocation Indicator Data Source Related to Human Population, Consumption, and Land Use Practices Demographics/Change in growth, including INEGI-Mexico fertility rates and a region’s demographic U.S. Census structure. Deficit of potable water supply (Vogel) (1+g/1+r) g= population growth r=supply growth (must include ground water storage, and surface water interaction/input) Per capita water use + allocation/acre Municipal utilities consumptive use Irrigation districts (EBID, EP#1, Distrito Riego 009) satellite imagery (Mexico) current land use maps Change in aquifer storage Change in depth to water over (rate of change) time. Well attribute data (WRRI, USGS, and NMOSE). Attempt to attain volume estimates (USGS,WRRI, UTEP, Texas A&M, UACJ). CNA and JMAS can provide data for Mexican border cities. Amount of groundwater pumped to meet Rio Grande Compact, NMOSE, demand, both agriculture and M&I Water Rights, EBID, EP#1, EPWU, and CONAGUA Vulnerability Source Economic sensitivity to water availability Indicator Water use by sector and revenue generated per direct economic use Data Source Las Cruces—MVEDA, LRGWUO, City of Las Cruces. El Paso—Ari Michelsen. Juarez— Lucinda Vargas, JMAS, and Rene Franco. Tijuana – CESPTijuana. Water Quality-Related/Human Health NAWQUA, NASQUON, NM Environment Department. Impairments to water quality Salinity DO 17 Comments/Additions i Satellite imagery relative per capita consumption for municipal use and per acre use for agriculture Irrigation data by different crops (at least trees versus row crops) Perhaps consider summer and winter statistical surface. We won’t have resources for modeling GWSW interaction for this study. This indicator ignores in-stream rights.i Comments/Additions Threats to public and environmental health Specific biological contaminants Vulnerability Source Flood risk Drought severity Fecal coliforms El Paso—TCEQ, EPWU, IBWC/CILA, and Texas Clean Rivers Program. Mexico— SEMARNAT/PROFEPA, INEGI, Mexican Universities Non-point agricultural contaminants, including CAFO, nutrients, and agricultural chemicals Land cover, crop type, and pesticide intensity; EPA data on feedlot and # of animals TCEQ, NMED, Dona Ana County, CESPTijuana, Junta Municipal de Agua y Saneamiento Bob Gilliam model at USGS No widespread systematic testing currently exists. Data from PAHO and U.S.-Mexico Border Health Commission may be helpful. Problem is linking disease with water quality Extent of hook-ups for sewage and potable water supply Sewage discharge/river discharge Nitrogen load Pathogens - enteroviruses, fecal coliforms, and cryptosporidium and their impact on morbidity and mortality Indicator Data Source Natural Events (Although effects are influenced by anthropogenic disturbance) % of stream class that is channelized Aerial photos/Digital images Status of aerial photo project along border? Tijuana-San Diego flood control project w/ COLEF, SDSU, and others % of impervious surface in watersheds Land cover/ satellite imagery and DEM’s, Tijuana-San Diego flood control project w/ COLEF, SDSU, and others Population in Floodplain FEMA, maps of urbanization # of times in past X years that drought severity CNA/NOAA /Prism (OSU) index has exceeded threshold value (rangeland communities) Coefficient of variation of streamflow FBOR, USGS, IBWC, CNA Ecological Concerns 18 Question remains as to how to link water quality measures to environmental health. Comments/Additions ii Reduction in riparian and aquatic ecosystems extent/composition Vulnerability Source Reduction in riparian and aquatic ecosystems extent/composition Threat to biodiversity – aquatic, terrestrial, and migratory Urbanization Infrastructure quality performance Infrastructure “brittleness” Series of landscape metrics from field counts, and remote sensing data Remote Sensing, Surveys, SWREGAP, Research literature, Fort. Bliss, University research, SEMARNAT, Mexican State, Federal, and, NGO data, INE. Explore potential use of ATtILAiii to examine spatial variability of landscape metrics Diversity Indicators Changes in # of species at risk Changes in # of extirpated Species Research literature, Universities, NGOs, Federal data (USFWS and INE), and state agencies Use of macro-invertebrates—more diverse. Indicator Degree of protected-ness Data Source SWREGAP Comments/Additions Amt of state/federally protected lands Adequate water flows for ecological needs Binational federal agencies and NGOs – RGRBBC & WWF. Quantitative changes in habitats NA models/GAP data Series of landscape metrics from field counts, Remote Sensing, remote sensing data surveys, SWREGAP, Fort Bliss, SEMARNAT, Mexican State, Federal, and NGO data, INE. Diversity Indicators Literature, Universities, Fort Bliss, Changes in # of species at risk SEMARNAT, Mexican State, # of Extirpated Species Federal, and NGO data, INE. Extent/Connectivity- Landscape metrics Land use change Potential use of ATtILA Hydrological response- sediment yield, surface DEM’s- soils cover-NALC-USGS runoff, percolation, change in land use (soils –differences between MexUS)-SWAT NRCS Issues related to infrastructure and Water delivery Age of network & condition Municipal utilities Transmission or conveyance and billing Irrigation districts efficiencies Agricultural efficiency Distance to water supply Sewer and water coverages from Redundancy of water supply municipal utilities and possibly Contingency plan Census data 19 Imperviousness also tied to ecological integrity Explore potential use of AGWA.iv Vulnerability Source Infrastructure “brittleness” cont. Indicator Adequacy of coverage in colonias in New Mexico, Chihuahua, and Texas Lack of adaptive capacity Per capita consumptive water use in I & M. Data Source TCEQ, NMED, Dona Ana and El Paso County Health Departments, and JMAS Municipal utility data % of total agriculture in permanent crops (examples are pecans & vineyards). Consumptive use over total extraction by sector Institutional potential for transfers and maturity of water markets Institutional capability and effectiveness Presence/absence, effectiveness, and comprehensiveness of water plan Financial capacity of water institutions (# and nature to be determined) Conjunctive management of surface and ground water resources Bond rating i Acreage data from irrigation districts Municipal utility data Irrigation district data Potential for transfers —ordinal ranking using institutional research literature, CNA & PRONAGUA CNA, JMAS, EPWU, and CLC Water Utilities Water plans themselves, research literature that critically reviews them, and master plans and data related to the BECC. Regional water plans, groundwater and surface water codes S+P and Moody’s ratings, rosters/Scorecards, and possible BECC data. Comments/Additions Transaction costs, import demand ratio, spending power, legal flexibility Performance measures Recognizing that some issues are not going to show variability at a sub-basin level, they are still important issues and should be included in any analysis of vulnerability. ii H. Passell – magnitude and duration of annual extreme conditions and 90-day means, or magnitude of monthly water conditions, or timing of annual extreme water conditions, or frequency and duration of high and low pulses, or rate and frequency of water condition changes. iii ATtILA is the USEPA GIS-based landscape metric tool discussed by William Kepner that has enjoyed wide use in the San Pedro Basin. The SCERP project staff is exploring training on this software to support this project. iv AGWA is the USEPA GIS-based tool for geo-spatial watershed assessment discussed by William Kepner that has enjoyed wide use in the San Pedro Basin. The SCERP project staff is exploring training on this software to support this project. 20 Table 2. Data Availability Assessment Data Availability Sub-Basin Vulnerability Source Indicator TRW Human Population Size of population Rate of population growth Population density Estimates can be obtained from U.S. & Mex. censuses U.S. & Mex. census date not available by sub-basin. Remote sensing methods required. INEGI data available Population Water Stress Deficit of potable water supply (1 + pop. growth/1 + supply growth) Pop. data and surface water data estimates OK. Poor data on ground water storage. Importation of water must be considered Pop. data and surface water data OK. Same data on ground water storage. Importation of water must be considered. Consumptive Use Per capital water use Estimates for U.S. from SDCWA and Co. of S.D. Not certain about estimate for Mex. rural areas. CESPT & CESPTE have data for Mex. urban areas. Pop. data can be obtained using remote sensing. Surface water data estimates OK. Poor data on ground water storage. Importation of water into some basins must be considered. Estimates for U.S. from SDCWA and Co. of S.D. Not certain about estimate for Mex. rural areas. CESPT & CESPTE have data for Mex. urban areas From CESPT and CESPTE To estimate this it could be hypothesized that total supply is equal to total consumption both in CESPT and CESPTE jurisdictions (total consumption is the addition of the volumes from each source plus the service looses). Total consumption per capita is therefore equal to total consumption divided by total population. Groundwater Overdraft Change in aquifer storage Poor data on changes in aquifer storage for most of watershed. Poor data on change in aquifer storage from most subbasins. Data available from CESPT and CESPTE Data are not reliable. The few records that might be available are scattered in time. These are usually developed by CNA (which is rather though when it comes to disclose its data). We 21 Tijuana/Tecate Comments from COLEF team Data at the locality and AGEB levels are available. Estimation of population for the Mexican part of TRW can be accomplished by doing calculations at the polygon level. It is necessary to define the time period of analysis. Supply data from CESPT are desegregated by source (i.e. Colorado River Aqueduct, wells, etc.). So the figure that interests us is the total. The same can be assumed from CESPTE. The only thing is to make sure that data are for at least 10 years in the past. Degree of OverAllocation Amount of ground water pumped to meet demand Poor data on ground water pumped for most of watershed. Poor data on ground water pumped for most sub-basins Data available from CESPT and CESPTE Economic Sensitivity to water availability Water use by industrial sector and revenue generated per use Data not available for entire watershed Data not available for most sub-basins Direct data may be obtainable from CESPT and CESPTE Impairments to water quality Salinity, do, fecal coliforms, non-point ag. contaminants Some data for lower watershed collected by Gersberg & others. Modeling using NURP data can be done Data not available for all sub-basins. Estimates can be obtained with modeling Some data available just downstream from Tijuana & Tecate from Gersberg Water pollution (public health-environmental health) Sewage hook-ups, potable water supply, health measures Data on sewage & potable water hookups available for Tijuana, possibly Tecate Data not available from most sub-basins Data on sewage and potable water hookups available for Tijuana possibly Tecate 22 (COLEF) have some information for the year 2000 CESPT and CESPTE have data only for those wells used by these agencies to meet their needs. For the rest we face the same problems above with CNA. At this moment there are no data at the municipal level. CESPT holds data on monthly water consumption by business and sector only (we do not know about CESPTE). One way is to estimate the numbers at the state level and assume that the same proportion holds for Tijuana (and Tecate if such is the case). The same conditions as in the case of groundwater overdraft apply here. Data are old and dispersed over time. Possible solutions would be to work with indicators on number of treatment plants, levels of treatment, and reuse volumes. Some studies have targeted the coast pollution and provide measures on organic pollutants and other contaminants for the Tijuana area which may be assumed to be present at the TRW level. Data on sewage and potable water coverage from CESPT and CESPTE are available (may be not for different points in time for the latter). These data only for urban Specific BioContaminants Flood Risk Drought Severity Disease, etc See impairments to water quality Compute from remotely sensed imagery See impairments to water quality Compute from remotely sensed imagery Percent of Impervious surface Compute from remotely sensed imagery or land use Compute from remotely sensed imagery or land use Percent of population in flood//plain FEMA maps & imagery from U.S. Imagery for Mex. FEMA maps & imagery for U.S. Imagery for Mex. No. of times that drought severity index has exceeded threshold valve Historical climate data Historical climate data Percent of stream class that is channalized Coefficient of variation of stream flow 23 See impairments to water quality Compute from remotely sensed imagery Compute from remotely sensed imagery or land use Compute from remotely sensed imagery Historical climate data areas. The 2000 population census from INEGI has these data desegregated to include the % of households that do not have access to water or sewage and rely on other strategies. Same comments as for impairments to water quality. Both institutions (SDSU and COLEF) have modeling systems that can estimate these types of indicators. They are currently monitoring one section of Arroyo Alamar to have more precise estimations. These measures can be extrapolated later at the watershed level. Historical data on temperature, precipitation and humidity may be obtained from CNA through its local or state offices. These data, however, are in hard copy and need to be integrated in digital form. Reduction in riparian ecosystem extent/composition Threat to biodiversity (not just riparian) Urbanization Landscape metrics Historical remote imagery Historical remote sensed imagery Historical remote sensed imagery Diversity indicators Data not available Data not available Data not available Degree of protected ness Percent of protected open space Percent of protected open space Percent of protected open space Same as riparian above Same as riparian above Remotely sensed imagery TRW GIS database Same as riparian above Remotely sensed imagery TRW GIS database Same as riparian above Use of ATtILA, AGWA, and other models Not relevant to most of TRW Use of ATtILA, AGWA, and other models Not relevant to most sub-basins Use of ATtILA, AGWA, and other models Data available from CESPT & CESPTE Data from SDCWA, CESPT & CESPTE for urban areas Data from SDCWA, CESPT & CESPTE for urban areas Data from CESPT & CESPTE Percent of urban land cover, growth of urban footprint Hydrologic response to urbanization Infrastructure quality performance Age and condition of water & sewage infrastructure Infrastructure “brittleness” Distance to water supply Redundancy of water supply Contingency Plan 24 Remotely sensed imagery TRW GIS database Landscape metrics: Data layers from Lina Ojeda’s work with estimates for surface by type of vegetation are available. Diversity: An indicator needs to be constructed. Sources are: Conabio, Semarnat (technical information on the Escalera Nautica project); Nature Conservancy (for Tecate), and Forest Inventory from Semarnat (1990 and 2000) Degree of protected ness: The most important part is the Estuary. The comments on diversity indicators apply also here. Data are available for the Mexican part of the Tijuana watershed. However, personnel training will be needed to construct this indicator. At the urban level, data are available from CESPT and CESPTE (potable water and sewage networks). In the case of infrastructure outside the cities, COSAE (State Commission of Water Services) and CNA itself have information on the operation conditions of the aqueducts in the state. Distance can be calculated from the GIS system. Contingency plan information is available from CESPT and CILA (urban zones). Tecate’s case is not clear. Percentage of water supply that is imported Per capita consumption of water use in M&I Data from SDCWA, CESPT & CESPTE from urban areas Data from SDCWA, CESPT & CESPTE for urban areas Data from CESPT and CESPTE Data at the municipal level. Best source is remotely sensed imagery Remotely sensed imagery Not relevant Agricultural uses are rather low in the watershed. An assumption should be made. This can be estimated from data from CESPT and CESPTE. Consumptive use over total extraction by sector Data not available Data not available Data not available Institutional potential for transfers and maturity of water markets This is difficult now because the current Law of Waters does not support it. ? ? ? Management indicators from CESPT and CESPTE. CESPT Master Water Plan progress evaluations. State Water Plan Info. from CNA, SDCWA, CESPT, CESPTE CESPT Master Water Plan State Water Plan % of ag. in permanent crops Lack of Adaptive capacity Presence/absence, effectiveness, and comprehensiveness of water plan Conjunctive management of surface and ground water resources Info. from CNA, SDCWA, CESPT, CESPTE Info. from CNA, SDCWA, CESPT, CESPTE Financial capacity of water institutions Vulnerability Source Precipitation Bond Rating Indicator Precipitation Variation Info. from CNA, SDCWA, CESPT, CESPTE TRW Interpolated Info. from CNA, SDCWA, CESPT, CESPTE Info. from CNA, SDCWA, CESPT, CESPTE Info. from CNA, SDCWA, CESPT, CESPTE Data Availability Sub-Basin Interpolated 25 Info. from CNA, SDCWA, CESPT, CESPTE Info. from CNA, SDCWA, CESPT, CESPTE Management indicators CESPT and CESPTE (municipal level) Tijuana/Tecate Local weather stations Comments Data on hard copy are available from CNA for Dependence on external sources of water Ratio of local water used to import water used Data from CNA, SDCUA, CESPT, & CESPTE Data from CNA, SDCWA, CESPT, & CESPTE where relevant Data from CESPT and CESPTE Sand & gravel extraction Areas in stream valley of sand and gravel extraction From remotely sensed imagery From remotely sensed imagery From remotely sensed imagery Stormwater prevention programs Areas covered by effective stormwater prevention programs RWQCB & CNA (?) RWQCB & CNA (?) RWQCB & CNA (?) Condition of sewage infrastructure Age of sewage lines SDCWA, CESPT, CESPTE, IB, City of S.D. SDCWA, CESPI, CESPTE, IB, City of S.D. CESPT, CESPTE Sewage Overflows No. & volume of sewage spills SDCWA, CESPT, CESPTE, IB, City of S.D. SDCWA, CESPT, CESPTE, IB. City of S.D. CESPT, CESPTE Soil Erosion & Siltation Susceptibility to soil erosion & siltation Model based on slope, cover, soil and precipitation Model based on slope, cover, soil and precipitation Model based on slope, cover, soil and precipitation Standard of living Per capita income INEGI, Bureau of the Census INEGI, Bureau of the Census INEGI 26 the region and the watershed. Ratio was .059 for 2001. Historical data from CESPT on this may be obtained for some time back. Only the locations where sand & gravel has been removed can be identified with remotely sensed imagery. At the urban level, CESPT and the Contingencies Direction in Tijuana At most, data are at the municipal level, from CESPT and CESPTE Don’t know exactly if CESPT in Tijuana has this kind of data updated ? Data for Tijuana on income is available from the Survey on Urban Employment (ENEU) by INEGI Table 3. Percent Impervious Surface by Sub-Basin Name Pine Valley Upper Cottonwood Lower Cottonwood Campo Creek Rio Seco Rio Tijuana El Florido La Cienega Las Palmas Las Canoas Las Calabazas El Beltran ISAT Results % Impervious Surface 2.36 2.5 5.42 3.71 3.63 39.18 5.6 2.73 3.51 2.38 2.72 2.39 Water Quality Protected Protected Protected Protected Protected Impacted Protected Protected Protected Protected Protected Protected 27 Englert (1997) % Impervious Surface 12 13 15 13 13 38 16 11 13 10 10 10 % Runoff 9 11 10 10 9 11 6 9 7 7 6 5 Table 4. Mexican portion of the Tijuana River Watershed. Water Availability 1991-2003 Year 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Water Total TRW (000's AF) 55.5 71.9 49.9 49.7 80.2 98.1 90 94.9 102.4 116.4 118.9 112.6 111 Imported Water (000's AF) Internal Water Sources (000's AF) Total % Total TRW Surface % Underground % 26.1 36.5 15.6 14.8 2.1 22.9 59.7 21.0 27.5 91.1 93.2 86.9 84.9 47.0 50.8 31.3 29.8 2.6 23.3 66.3 22.1 26.9 78.3 78.4 77.2 76.5 23.3 39.3 13.9 12.9 0.0 20.3 58.2 20.1 26.6 89.7 91.4 85.8 83.6 89.5 107.7 89.4 87.1 0.0 88.5 97.5 95.7 96.7 98.4 98.0 98.7 98.4 2.8 2.8 1.6 1.9 2.1 2.6 1.5 0.9 0.9 1.5 1.9 1.1 1.3 10.6 7.8 10.4 12.6 100.4 11.3 2.4 4.2 3.2 1.6 2.0 1.3 1.5 Total % Total CRT Surface % Underground 29.4 35.4 34.3 34.9 78.1 75.2 30.3 73.9 74.9 25.3 25.7 25.7 26.1 53.0 49.2 68.7 70.2 97.4 76.7 33.7 77.9 73.1 21.7 21.6 22.8 23.5 4.7 10.7 9.6 10.1 53.3 50.4 5.6 49.2 50.2 0.6 1.0 1.0 1.4 16.0 30.2 27.9 29.0 68.3 67.1 18.5 66.6 67.0 2.2 3.8 3.8 5.3 24.7 24.7 24.7 24.7 24.7 24.7 24.7 24.7 24.7 24.7 24.7 24.7 24.7 % Total population TRW AF/ person Urban population TRW AF/ person 84.1 69.8 72.1 70.8 31.7 32.9 81.6 33.5 33.0 97.7 96.2 96.2 94.7 791069 830622 872154 915761 961549 1009627 1060108 1113113 1168769 1240150 1302158 1367265 1435629 0.07 0.09 0.06 0.05 0.08 0.10 0.08 0.09 0.09 0.09 0.09 0.08 0.08 775942 814739 855476 898249 943162 990320 1039836 1091828 1146419 1201075 1261129 1324185 1390394 0.07 0.09 0.06 0.06 0.09 0.10 0.09 0.09 0.09 0.10 0.09 0.09 0.08 Population projections based on the 1990-2000 annual growth rate for the Mexican portion of the TRW. Sources: Comisión Estatal de Servicios Públicos de Tijuana (CESPT), Total Water Supply 1991-2004; Comisión Estatal de Servicios Públicos de Tecate (CESPTE), Total Water Supply 1995-2005; Comisión de Servicios de Agua del Estado de BC (CEA), Mexicali-Tijuana Aqueduct annual supply, 1985-2003; Comisión Estatal de Agua de BC (COSAE), State Water Plan 2003-2007; INEGI, Mexican Population Censuses 1990 and 2000. 28 Table 5. U.S. side of the TRW. Water availability, 2000-2004 City of San Diego Year Total Supply (AF) Otay Water District Total Supply (AF) Total Pop.* AF/Person Local SDCWA 1999 53,135.30 169,790.00 1,224,848 2000 33,909.80 206,434.20 2001 24,794 2002 Total Pop.* AF/Person Local SDCWA 0.18 896.7 25,442.30 116,800 0.23 1,277,168 0.19 944.2 29,901.20 123,420 0.25 200,648 1,282,532 0.18 850 30,002 124,099 0.25 23,562 204,527 1,287,919 0.18 971 35,182 124,782 0.29 2003 22,914 192,641 1,293,328 0.17 1,013 34,535 125,468 0.28 2004 11,119 227,220 1,298,760 0.18 1,277 39,579 126,158 0.32 * Population projections for 2001-04 were made using the 1990-2000 annual growth rate for the corresponding service areas. Sources: SDCWA Annual Reports 1999-2000, 2000-2001, 2001-2002, 2002-2003, 2003-2004. Table 6. TRW Water Availability Indicators 2000-2004 Mexican portion Year U.S. portion Total water availability (AF) Total population AF per capita AF per capita City of San Diego AF per capita Otay Water District 1999 102400 1168769 0.09 0.18 0.23 2000 116400 1240150 0.09 0.19 0.25 2001 118900 1302158 0.09 0.18 0.25 2002 112600 1367265 0.08 0.18 0.29 2003 111000 1435629 0.08 0.17 0.28 2004 N.A. 1507410 N.A. 0.18 0.32 Sources: Tables 1 and 2. 29 30