1
Monthly Time Step WRAP Modeling Using
Environmental Instream Flow Requirements
Ramiro Martinez and Dr. Ralph Wurbs, M. ASCE1

Abstract— The Water Rights Analysis Package (WRAP) model
simulates management of the water resources of a river basin or
multiple-basin region under a priority-based water allocation system.
Utilizing WRAP with basin-specified input files for the Brazos basin,
one may simulate a water availability model which predicts the
amount of water that would be in a river under a specified set of
requirements. The Brazos River Authority (BRA) has submitted a
permit which has various instream flow requirements. To model these
instream flow requirements text must be translated to records within
the Brazos dataset. Once appropriately interpreted into the dataset
one may use the SIM-TAB option within WRAP to simulate and
tabulate the Brazos basin and the various effect that the instream flow
requirements may have. These requirements means more water
instream and less water being allocated. Modeling these requirements
could give us a better understanding of the risks produced in volume
and periodic reliability.
Index Terms—Water Rights Analysis Package, water
allocation, Brazos River Authority, environmental instream flow
requirements.
I. INTRODUCTION
A
lthough water is an important factor of everyday life,
many places on earth consider having readily available
water a privilege instead of a commodity. In these parts of the
world, governments have taken the responsibility of allocating
this precious resource by means of importance. In order to
estimate the importance of one specific element, all of the
elements being considered must be recognized within a water
allocation model. In Texas a Water Availability Modeling
system (WAM) was implemented during 1997-2004 by the
Texas Commission on Environmental Quality (TCEQ) under a
mandate provided by comprehensive water management
legislation enacted by the Texas legislature in 1997 (Wurbs
2005). Soon after this establishment the WAM system became
a standard for any water allocation modeling within Texas.
Manuscript received August 2, 2011. This work was supported in part by
the Undergraduate Summer Research Grant Program.
Ramiro Martinez is currently a student research assistant under the
Department of Civil Engineering at Texas A&M University, College Station,
TX 77840 USA (phone: 956-266-5975; e-mail: ram_arrow@neo.tamu.edu).
Dr. Ralph Wurbs is a professor under the Department of Civil Engineering
at Texas A&M University, College Station, TX 77840 USA (e-mail:
ralph@civil.tamu.edu).
From then on TCEQ took the responsibility of reviewing
water permit applications throughout Texas. In order to
establish a diversion from the Texas surface water, one must
submit a water permit application. The TCEQ organizations
then approves or rejects the application. In Texas alone there
are about 8,000 permits on the use of surface waters which
have been granted to river authorities, irrigation districts,
municipal water districts, cities, private companies, and
individual citizens.
The WAM system consists of the Water Rights Analysis
Package (WRAP) model, 21 sets of WRAP input files
covering the 23 river basins of the state, a geographic
information system (GIS), and other supporting databases
(Wurbs 2005). Although WAM is initially only used in Texas,
these water allocation modeling systems can be apply
anywhere else. The WRAP model simulates management of
the water resources of a river basin or multiple-basin region
under a priority-based water allocation system (Wurbs 2006).
However, for WRAP to simulate a river basin it must contain a
dataset and the accommodating files. Most of these datasets
can be found online at the TCEQ website.
For each river basin there are two types of datasets, full
authorization and current conditions. For the purposes of this
study, the only dataset used will be the full authorized version
of the Brazos River Basin. These datasets consist of many
records, lines of data, which deliberate each water right or
environmental instream flow requirement that is implemented.
When introducing a new water right to the dataset a priority
date is set, usually the date the permit application was
submitted. This means that any water rights inducted before
this date have seniority over the new water rights.
The Brazos River Authority (BRA) submitted a permit
application, No. 5814, to the TCEQ on October 2004. The
permit, if passed, will allow BRA to divert water from the
Brazos river and the specified reservoir. TCEQ has given the
BRA a set of environmental instream flow requirements which
they must meet so that this permit may be passed. This study
aims to interpret those instream flow requirements from the
BRA permit to a set of records within the Brazos River Basin
dataset.
The Brazos River Basin dataset contains thousands of
control points which identify the direction of flow within the
basin. Throughout the basin there are less than one hundred
primary control points where the U.S. Geological Survey
(USGS) have setup gaging stations. These gaging stations
monitor the stream flow, water height, discharge, water
chemistry and water temperature. The new permit has decided
to setup its environmental instream flow requirements at
JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JUNE / JULY 2011
2
certain USGS control points, which are beneficial to monitor
the stream flow daily and ensure the requirements are upheld.
Due to time constrains this study focused on instilling only the
environmental base flow requirement for the gaging station at
Richmond. The control point at this location is BRRI70.
II. BACKGROUND
The permit being present by the Brazos River Authority has
provided environmental instream flow requirements at about
sixteen USGS gaging stations. Although there are not many
gaging stations the instream flow requirements are complex
and require many sets of records in order to implement the
different flow types and hydrological conditions. Although this
study will only be focusing on one base flow requirement,
there are three flow types within the permit, base, pulse and
peak flow. A base flow is the amount of water entering a
stream channel from groundwater sources. Usually base flows
are consistent over long periods of time. A pulse flow is the
amount of water entering a stream channel during a period of
rainfall. A peak flow is the amount of water entering a stream
channel during a very short period of time where rainfall is at
its highest.
Each of these flow types are then given a hydrological
condition for every month of each year within the period of
analysis. The Brazos River Authority permit has decided to
categorize flows into four different hydrological conditions
which depend on the amount of total storage (TS) the specified
reservoirs provide. Each month of the years simulated and
given a hydrological condition: wet (>96% of TS), average
(96-74% of TS), dry (74-60% of TS), and subsidized (<60%
of TS). The base flow requirement at BRRI70 is described in
Table 1 below.
Table 1.Environmental base flow requirement at Richmond Gage
Instream Flow
BRAZOS RIVER NEAR RICHMOND - USGS
(cfs)
#08114000 (BRRI70)
Winter
Spring
Summer
Fall
Subsistence
(7Q2)
Dry
743
743
743
743
885
1170
930
760
Average
1630
2030
1450
1150
Wet
2955
3670
2635
2038
Unappropriated flows are flows within the stream channel
that have not been allocated to a certain water right. In the case
of environmental instream flow requirements, the flow is not
considered an unappropriated flow because it is being used to
sustain the environmental habitat of the stream.
The new permit allows water to be diverted from only
specified reservoirs: Possum Kingdom Lake, Granbury Lake,
Whitney Lake, Aquilla Lake, Limestone Lake, Proctor Lake,
Belton Lake, Stillhouse Hollow Lake, Georgetown Lake,
Granger Lake, Somerville Lake. And Allens Creek.
III. METHODOLOGY
The instream flow requirement being setup requires a
certain flow (cfs) which depend on the hydrological conditions
and seasons of a certain year. Since WRAP only reads values
in ac-ft/month the values must be converted and estimated into
monthly values. These monthly target values where then
written into WRAP using UC records.
Next the hydrological conditions for each month were
calculated by running the original Brazos dataset. Tables
containing storage values for the reservoirs specified were then
calculated using the Tables option within WRAP. These
reservoirs where then tallied up to construct the total reservoir
storages. Using these total storage values, percentiles were
sought and then hydrological conditions were set to each
month depending the their percentile count. Each month was
given a value between 1-4 depending the condition. These
hydrological conditions where then inserted into the dataset
using TS records under a pretentious water right at an isolated
control point. This had to be done so that the correct
hydrological condition could be matched with the right flow
requirement depending on the month from the UC records.
Finally an IF record was inserted into the dataset. This
record is solely responsible for applying a real environmental
base flow requirement at BRRI70.
Since this new requirement will be junior to all other water
rights a water right diversion was inserted to understand the
effects of this new requirement.
IV. RESULTS
When implementing the new water right diversion which
was junior to all other water rights, there was a decrease in
unappropriated flows and in regulated stream flows. Both of
these decreases were only when the new water rights target
diversion was met or partially met. The difference was always
the same as the target met that month by the water right.
Figure 1. Unappropriated flows at Richmond Gage. A comparison
between the original dataset and new dataset with requirement.
When the base flow requirement was activated there was an
even lower decrease in unappropriated flows, due to the fact
that these flow were being used by the environment. The water
right diversion junior to the requirements also decrease due to
the lack of unappropriated flows. The difference within the
flows has been depicted in Figure 1.
JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JUNE / JULY 2011
3
V. DISCUSSION
Although this study has successfully implemented an
environmental instream flow requirement for the base flow at
the Richmond gage, environmental instream flow requirements
for base flows, pulse flows, and peak flows for the other
gaging stations must still be developed and applied to the
Brazos dataset. Once all these requirements have been set at
the Richmond gage, these exact records could easily be
applied to other gaging stations using their own hydrological
conditions and set of UC records.
The reason the Richmond gage was chosen to start off with
was because out of all the USGS stations chosen by the permit
the Richmond gage was the furthest down the river basin.
After the preceding objectives have been met, the next step
would be to replicate these requirements in the daily time step
dataset of the Brazos River Basin.
Another possible project that could be worked on is
developing a more concise set of records in order to decrease
the simulations run time. WRAP’s flexibility provides many
ways of compressing sets of records. Although compressing
records might help, the reason this wasn’t seen further through
was because of time constraints and much of the simulation
time depends on the number of control points within the
model.
ACKNOWLEDGMENT
Ramiro Martine would like to thank the Undergraduate
Summer Research Grant Program for providing this great
opportunity to further my research experience this summer. He
also would like to thank Dr. Wurbs in mentoring him and
being patient with him when things might not have gone as
planned.
REFERENCES
[1]
[2]
[3]
[4]
[5]
Brazos River Authority (2004). “Water Permit Application: No. 5814.”
Texas Commission on Environmental Quality.
Wurbs, R. A. (2010a). “Application of Expanded WRAP Modeling
Capabilities to the Brazos WAM.” Tech Rep. 389, Texas Water
Resources Institute, College Station, Tex.
Wurbs, R. A. (2010b). “Fundamentals of Water Availability Modeling
with WRAP.” Tech Rep. 283, Texas Water Resources Institute, College
Station, Tex.
Wurbs, R. A. (2003a). “Water Right Analysis Package (WRAP) modeling system reference manual.” Tech Rep. 255, Texas Water Resources
Institute, College Station, Tex.
Wurbs, R. A. (2003b). “Water Right Analysis Package (WRAP) modeling system users manual.” Tech Rep. 256, Texas Water Resources
Institute, College Station, Tex.
JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT © ASCE / JUNE / JULY 2011