SALINITY STUDY GUIDE Supporting Stage 5 & 6 Geography Table of Contents 1. Important stuff Page 2 2. Extent of problem Page 3 3. What is salinity? Page 4 4a. Sources of salt Page 5 4b. Impacts Page 6 5. Water Cycle Page 8 6. Recharge and discharge Page 9 7. Catchments Page 10 8. Sub-catchments Page 11 8a. Case study : Livingstone Creek Page 13 9. Causes: natural Page 15 10a. Causes: farming Page 16 10b. Causes: urban Page 16 11. Management: Preparing for a field investigation Page 17 12. Measuring salinity Page 18 13. Investigation: water tables Page 19 14. Piezometers Page 21 15. Salinity indicators: plants Page 22 16. Salinity indicators: landscape Page 24 17. Salinity indicators: urban Page 25 18. Salinity classification Page 26 19. Investigation: how bad is salinity at this site? Page 28 20. Investigation: where does salinity occur in Wagga Wagga? Page 30 21. Research Resources and Internet links Page 32 Page | 1 1. Important Stuff Water Cycle The height of the water table is a balance between inputs and outputs of water to the groundwater. 1. Dryland salinity Occurs in dryland farming areas (non irrigated farming). The land has been cleared of many trees and outputs of water via transpiration from trees decreases so the water table rises. 2. Irrigation salinity Occurs in irrigation farming areas. Inputs of water increase from irrigation and the water table rises. 3. Urban salinity Occurs in towns. Inputs of water increase from watering gardens, playing fields and parks and leaky water pipes. 4. Natural risks Some areas have naturally high water tables and are saline and have been since recorded history. This can be caused by natural features such as catchment shape, changes in soil permeability down a hill or extended periods of higher than normal rainfall. Page | 2 2. Extent of the problem "Every day, another chunk of land about the size of a football field is quietly drowning in salt. By the time a baby born today reaches the age of about 30, a total area almost equivalent in size to the State of Victoria will have gone under: dead, useless, ugly, awkward, embarrassing and depressing." Michael Archer and Bob Beale, Going Native, 2004 (Figures quoted are current best estimate.) Salinity is a big problem in Australia. The map is a forecast of areas with salinity by the year 2050. Map: Commonwealth of Australia, 2001, Dryland salinity in Aust..... Assess. Some 2.5 million hectares of rural land are already affected by salinity, and there is the potential for this to increase to 15 million hectares. Much of this is Australia 's most productive agricultural land. The area damaged by salinity to date represents about 4.5 percent of present cultivated land. CSIRO Salinity is also a world problem. The world map shows countries which are investigating salinity. There are currently 77 million hectares of salinised land caused by human activities. Page | 3 3. What is salinity? Salinity occurs when salty groundwater is close to or at the surface of the soil. When the water table is within two meters of the surface it is within the root zone of many plants. Air pores in the soil act like a sponge and the salty water is drawn up to the soil surface. This is called capillary rise. Damage to buildings, roads and plants is usually a combination of salt and waterlogging. There are different causes of salinity: dryland salinity; irrigation salinity; and urban salinity. This study is concerned mainly with urban and dryland, not irrigation salinity. Page | 4 4a. Where does the salt come from? The salt in groundwater can come from: rainfall (cyclic salt in the water cycle) the weathering of rock including old sea sediments wind blown (Aeolian) salt crystals from oceans and salt lakes Scientists estimate that 15 kilograms of salt per hectare enter the soil each year in South Eastern Australia. If the water table rises, salt crystals in the soil will be dissolved and enter the groundwater. Once the salt is dissolved in the groundwater, the salt goes where the groundwater goes. Page | 5 4b. Impacts: damage Is this the future? Photo: Dept. Conservation, Forests and Lands Vic.brochure "Soil Salting" 1987 buildings Page | 6 former football field infrastructure: roads and steel water pipes dryland salinity: farming Photos courtesy of: Department Infrastructure, Planning, Natural resources Wagga Wagga Projection Below is the projected cost of the financial impact of salinity if no action is taken over the next 30 years. Page | 7 Item Water infrastructure House costs Sewerage pipes Gas pipes Agriculture Parks and sports grounds Septic tanks Footpaths Present value $87 883 000 $56 198 000 $8 308 000 $5 782 000 $3 586 000 $850 000 $714 000 $66 000 Total $163 387 000 5. Water cycle: water table movement The height of the water table changes as the amount of water entering it (inputs) and leaving it (outputs) changes. After a period of rainfall, water may enter the groundwater and the height of the water table rises. After a dry period, the water table may fall as the groundwater slowly drains down the catchment. The height of the water table is a balance between inputs and outputs of water to the groundwater. Activity: Compare the water table depth under natural conditions to when we have dryland farming and urban development in the diagram above. Conditions Natural Conditions Dryland Farming Urban Development Page | 8 Water Table Depth 6. Recharge and discharge Soil and rock which allows water to soak in quickly is permeable. In these parts of the landscape, rainwater can infiltrate down and enter the groundwater. These are recharge areas. Discharge areas occur where the water table is at or close to the surface. In the diagram the movement of groundwater is slowed by a clay barrier. The groundwater builds up behind it and is forced to the surface, creating a discharge area. Page | 9 7. Catchments Catchments are areas of land which drain water to their lowest parts. There are two important parts to this definition. 1. An area of land. How we use the land is very important. Trees cleared in upper catchments can cause water tables to rise lower in the catchment. 2. Drain water to the lowest parts. Water connects the different parts of a catchment. Water will transport things from upper to lower parts of catchments. Salt dissolved in groundwater will go where the groundwater goes. To solve salinity and other environmental issues we need to manage whole catchments, not just little parts. One town or one farm upstream can cause problems for others downstream. Satellite image: Australian Greenhouse Office The satellite image above shows a section of the Murrumbidgee catchment with three of its sub-catchments. Dark green/brown represents areas of remnant vegetation (natural bushland). Lighter colours, brown/white, indicate cleared farming areas. There are very few areas of deep rooted, natural bushland left which would use groundwater through transpiration, causing water tables to rise in lower catchment areas. Page | 10 8. Sub-catchment salinity Over 410 000 tonnes of salt pass Wagga Wagga each year, dissolved in the waters of the Murrumbidgee River. The Murrumbidgee flows into the Murray River and down to Adelaide which takes about 30% of it's drinking water from the Murray. At present the salinity of the Murray near Adelaide is over the 830 EC threshold for desirable drinking water some of the time and within a few years it is predicted it will be much worse if nothing is done. To fix the problem, land managers need to know where the salt is coming from. Researchers' in the Wagga Wagga area have been testing sub-catchment creeks of the Murrumbidgee. The worst catchments have been identified, so that land degradation problems which cause salinity can be targeted and the catchments managed on an ecologically sustainable basis. Page | 11 Below are some of their results. Catchment Murrumbidgee Yass R. Jugiong Muttama Kyeamba Characteristic (Wagga Creek Creek Creek Wagga) Water salinity (EC) 100 451 838 858 480 River salt load (kg/day) 1 126 027 29 851 60 012 19 314 1 977 The salinity of the Murrumbidgee is low (100 EC) but its large volume means the river transports a lot of salt each day. Salinity units used are EC's (electrical conductivity). The Kyeamba sub-catchment within the Murrumbidgee catchment has been divided into smaller catchments again and the salt content of flowing creeks was measured. From this we can get an idea of the land areas contributing the most salt to the creeks. This shows the salt problem is not even across the landscape. Map courtesy Department Infrastructure, Planning, Natural resources Page | 12 8b. Catchment case study: Livingstone Creek An understanding of the movement of salt through a catchment is important so the best remedial measures are used to fix salinity problems. Most salt movement in a catchment occurs as dissolved salt in water, scientists need to know how the water cycle works at a particular place because where the water goes, the salt goes. The Livingstone Creek sub-catchment covers 7% of the area of the Kyeamba catchment but contributes up to 70% of the salt load in Kyeamba Creek. A study of the landform, geology, groundwater and streamflow of the Livingstone subcatchment explains it's salt problem and the best way to fix it. Page | 13 The hilly, upper catchment has fine grained metamorphosed sedimentary rock (meta-sediments) which release salt when weathered. A band of hard granite rock which weathers slowly constricts the middle catchment so all water has to move through a narrow area. The lower catchment opens up to flatter, deeper, alluvial (stream) deposits. The groundwater can move deep into the meta-sediments where it dissolves the salt from the rock and then forms an underground salty lake. The granite blocks the movement of groundwater and forces it to the surface into the creek. Once the salty creek and groundwater have passed the granite it moves into the alluvium of the lower catchment causing salinity problems there. The salty creek and groundwater then leave the Livingstone Creek sub-catchment into the main Kyeamba catchment. To manage the salinity problems of the lower Livingstone Creek and Kyeamba catchments, land managers need to fix the problem at the source of the salt in the meta-sediments in the upper catchment. Measures taken further down will not stop the continual addition of salt from the meta-sediments. Note: The 'Big Springs', natural spring water company collects water from the granite area at the northern end of the catchment. The water cannot penetrate the granite which has little salt and runs off quickly and so is very fresh with little salt. “The waters of Big Springs are absorbed by the granite soils of the Flakeney Ranges and run through aquifer and underground channels that are filtered naturally through sands and gravels” http://www.bigspringsriverina.com/history.asp Page | 14 9. Natural risks Some areas have naturally high water tables. Human impacts often make natural problems worse. Discharge area occurs at change in slope. Large volume of groundwater from a broad catchment is "squeezed" at the catchment mouth. Page | 15 Groundwater builds up behind less permeable soil. Groundwater is forced to go over a bump in the basement rock. This is a contributing factor to salinity in some of the large irrigation areas along the Murray River. 10a. Causes: dryland farming Clearing deep rooted bushland and replacing it with shallow rooted pasture grasses and crops has led to more rainwater making its way into the groundwater. Compare the map of dryland salinity with the satellite image showing the area of native vegetation cleared in red. 10b. Causes: urban Increased inputs into the groundwater: Watering of gardens and recreational areas such as parks and sporting areas. Leaking pipes such as water supply pipes. Rainwater from roofs run into rubble pits in the ground instead of surface gutters. Page | 16 11. Management Sources of groundwater recharge (Wagga Wagga Urban Pilot Study) Rainfall 22% Rubble Pits 14% Leaky water pipes 47% Leaky sewer pipes 12% Garden watering 5% Urban area solutions Engineering: Install bores in trouble spots and pump the water out. Wagga Wagga has nine de-watering bores which automatically pump out groundwater when the water table is within 2.5 metres of the surface. Deep drainage. Sub-soil drainage has been installed at the Wagga Wagga Showground to stop the water table rising to the surface. Take rainfall runoff from roofs into street gutters instead of putting it into rubble pits in the ground. Repair leaky water pipes. Educational: Encourage residents to place timers on garden sprinklers and plant "waterwise" gardens. Dryland farming solutions Plant trees and shrubs in recharge areas. (Trees pump the groundwater out and shrubs intersect soil moisture from rain before it reaches the water table. Replace shallow rooted pasture grasses with deep rooted varieties. Catchment management as well as farm management since salinity crosses farm boundaries and is a catchment scale problem. Landcare educational programs. Note: It is not possible to fully treat management in this study guide. The Department of Infrastructure, Planning and Natural Resources (DIPNR) has an excellent web site. See 'Links" at the end of this study guide. Page | 17 12. Measuring salinity Most meters measure the electrical conductivity of water. Batteries are connected to two wires (electrodes). Salty water will conduct electricity between the two electrodes, the saltier the water, the more electricity is conducted. The unit of electrical measurement used is Siemens. The meter we use in the field measures milliSiemens (mS) per centimetre (the electrodes are one centimetre apart). Often the literature will use microSiemens (uS) and EC standing for electrical conductivity. These two units are the same. To convert milliSiemens to EC's or uS multiply the reading by 1000. The meter in the diagram shows 1.65 mS which is 1650 uS or EC's. Water Salinity Levels for Use Source/Use uS/cm or EC distilled water 0 Source uS/cm or EC limit poultry 5 800 Murray R. (mouth) 790 limit beef cattle 16 600 desirable limit people 830 limit adult sheep 23 000 absolute limit people 2 500 Pacific Ocean 58 000 Conversions deciSiemens per meter (dS/m) = milliSiemens per cm (mS/cm) times by 1000 equals microSiemens per cm (uS/cm) = Electrical Conductivity units (EC's) Example 1.5 dS/m = 1.5 mS/cm = 1500 uS/cm = 1500 EC Care of the meter Turn the meter off after use. Only place it in the water 2 cm. Don't put the electrodes in mud. If is accidentally dropped in the water please let your teacher know. Page | 18 13. Investigation: water table changes Aim How does the planting of trees impact on the water table in a dryland salinity discharge area? Method Plant 4 000 eucalypts at a spacing of one tree every 3 metres. Monitor water table changes over several years with a piezometer. Monitor tree growth and record rainfall. Results Salinity area eucalypt plantation 2002 Page | 19 Salinity area eucalypt plantation 2003 Salinity area planted with trees with piezometer in 2004. Graph and photos courtesy Department Infrastructure, Planning, Natural Resources Wagga Wagga research centre Discussion Did the height of the water table change (dynamic) or stay the same (static) over the study period? Suggest reasons for the higher water table in winter each year. Describe what the red lines in the graph represent and explain why they became steeper over the three years. Describe what happened to the number of leaves on each tree as they grew older. What was the impact of the trees on the height of the water table? Page | 20 14. Piezometers Piezometers are holes bored into the ground which give access to the groundwater so the height of the water table can be measured and samples of groundwater obtained for testing for salt concentration. The bore holes are lined with plastic pipe which is protected above ground by a metal casing shown on right. The graph of the piezometer shows the seasonal water table movement at the DIPNR Research Centre salinity site from the previous page. Page | 21 15. Indicators of salinity Plant indicators Page | 22 Swampy couch Sea barley grass Spike rush Salt bush Some plant species can tolerate high salt concentrations and grow in these areas while others can only live in lower concentrations. Zones or concentric circles of plants can be seen in some areas indicating a change from high to low salinity. Succulent plants such as some salt bushes often grow in saline areas. These plants usually indicate dry conditions but salinity areas have high water tables. Plants rely on obtaining water through their roots. This depends on water naturally moving by osmosis from an area of lower salt concentration, usually in the soil, to one of higher salt concentration, found in plant cells. When the soil water is saltier than the plant cells, the plants can't obtain water by this method and may die from lack of water. Page | 23 16 Salinity indicators Landscape indicators Dead Trees Bare patches Clear Water Puffy soil with salt crust when dry Photos courtesy Department Infrastructure, Planning, Natural Resources Trees often die from waterlogging, their roots no longer able to breath. Bare patches occur where the salt concentration is too high for plants to grow. Salt dissolved in pools of water causes the clay particles suspended in the water to clump together and sink to the bottom, making the water clear (except for algae). A salt crust may be seen when the soil is dry and it may feel "puffy" when trodden on. Page | 24 17 Salinity indicators Urban indicators Steel infrastructure Salt line on bricks House water pipes Breakdown of road surface Photos courtesy Department Infrastructure, Planning, Natural Resources White markings on the surface of bricks formed from water evaporating, leaving salt crystals behind. Steel in contact with ground rusting more than normal. Breakdown of road surface caused by the saturation of the underlying soil and roadbase. Page | 25 18. Salinity classification Class 1. Earliest visible signs of salting are when the water table has started to move salts into the root zone. Soil salinity (1:5 soil/water mix) 2000 to 4000 EC. Signs to look for: boggy areas; reduced crop yield; patches of salt tolerant plants such as sea barley grass and couch. Class 2. Moderate salting occurs where the water table is at the surface for extended periods. Highly salt tolerant plants present. Soil salinity 4 000 to 8 000 EC. Page | 26 Signs to look for: scattered bare patches (up to 1m2); salt crystals on surface when dry; pools of water are clear; normal grasses replaced by sea barley grass, couch, beard grass, plantain and other salt tolerant species. Class 3. Severely affected areas have extensive scalding (bare areas) areas and the presence of salt loving plants (halophytes). Soil salinity over 8 000 EC. Signs to look for: extensive areas of bare ground with salt crystals when dry; salt loving succulents; sheet and gully erosion on sloping land. Soil salinity test: place 1 part soil in 5 parts water and shake to dissolve any salt in the soil then test solution with salinity meter. Page | 27 19. Investigation: how bad is salinity at this site? Use your knowledge to investigate salinity at this site. Page | 28 Activity: Aim Write a report on your investigation using the following headings. The purpose of your investigation. Methods Survey the area for plant and other indicators of salinity by dragging and dropping the red 1m2 quadrat frame on the site being investigated. Record the species of plants and other salinity indicators in each quadrat. The white transect line is 30 metres long. The survey needs to be carried out in a manner so we have confidence that the data collected is accurate. The quadrat needs to be dropped randomly on the survey site. You need to study enough quadrats to be sure you have surveyed the whole area. Do five quadrats. There is a transect line you may wish to use (it is fixed). Results Include a table of the data collected. Quadrat % bare % succulents % sea barley % couch One Two Three Four Five Discussion/conclusion What did you find out? How would you improve this investigation? Is there other data or equipment you would have liked access to? Page | 29 % doc 20. Investigation: how does water table height vary in Wagga? Aim Some residents have commented that their rose gardens and lawns have been dyeing so Wagga Wagga City Council have contracted you to investigate the water table height in an area of Wagga Wagga and write a report. Method Research existing GIS (Geographic Information Systems) data which has the location of piezometers and their readings. You now need to analyse your results. Air photo courtesy Department of Lands Piezometer Land surface height (m) 1 2 3 4 5 6 7 8 9 10 11 12 193 195 200 198 200 212 195 210 221 203 216 217 Ave. water table height (m) 0.1 1.0 4.9 11.6 0.1 12.8 1.8 7.9 12.4 5.3 7.0 12.2 Ave. salinity (EC x100) 67=6 700 EC Page | 30 67 63 63 174 43 37 52 171 77 25 87 35 Results Look for relationships between location, landform height, water table height and salinity. Display these in graph form. Draw a salinity hazard map where water tables are within 2 metres of the surface. Use the vertical air photo to comment on land use. Conclusion/discussion What do the results indicate? How could you improve this investigation? is there any equipment or additional data that would help? Page | 31 Research Resources Why Wagga has salinity (pdf 218 KB) Dryland salinity in Wagga (pdf 118 KB) Managing salinity in Wagga (Word 30 KB) Urban Salinity (Murrumbidgee CMA Word 23 KB) Map Wagga salinity bores (JPEG 86 KB) Map salinity in Wagga (JPEG 53 KB) Dryland Salinity (193 pages pdf 815 KB) River Murray, A Salinity Perspective (CSIRO pdf 190 KB) Salinity National Action Plan (pdf 239 KB) Links Department of Infrastructure Planning and Natural Resources * highly recommended (do a salinity search) www.dipnr.nsw.gov.au Murray Darling Basin Commission www.mdbc.gov.au Land and Water Resources Research and Development Corporation National Dryland Salinity Program www.lwrrdc.gov.au/ndsp/ Page | 32