III BASINS 2.0
VI Conclusions
VII References
Back to Jonu Finndisar homepage
Clean water is essential for all of us. However, because of a dense population in a state like Texas it is difficult to keep all surface water as clean as would be preferred. Therefore regulations have to be set to ensure the quality of Texas Surface Water. The State of Texas has established standards to guard the surface water, how it is used and measurements to keep track of whether the water is clean enough for the certain use. The Texas Natural Resource Conservation Commission (TNRCC) in association with other agencies divides rivers and lakes into "Water Quality Segments" for the purpose of monitoring the quality of water as a whole for each part. The segments are listed on a so-called 303(d)-list and if the water in a segment fails to meet water quality standards, a procedure to clean this segment has to be defined.
The project of defining Water Quality Segments, evaluating the cause of pollution and produce methods to clean the segments which do not meet the quality standards is called "Total Maximum Daily Load" (TMDL). Since developing TMDLs requires a watershed-based approach where both point and nonpoint sources are integrated, an environmental analysis system like BASINS 2.0 is useful.
Currently the water quality issues of Trinity River Basin in east Texas are being considered and my research project is a part of a Total Maximum Daily Loads project on the Trinity River. Since the product of my research project will be used in a similar way as the BASINS system, a quick inspection of the system will give a better overview over my research.
In this report I will define the study area for the survey of BASINS, then explain to a certain extent what the BASINS system consists of and show how to, and what came out of running the nonpoint source model NPSM on the study area. Finally, will I give some conclusions of my experience of BASINS.
The Trinity River Basin is located in East Texas and has approximately 18,000 square mile area. In the northwest part of the basin the altitude is 1,200 feet and the terrain varies from hills and valleys to prairies with grasslands and farms. The central part of the basin is hilly, while the lower part is plain. The Trinity River opens into the Trinity Bay and from there the water flows into the Galveston Bay, which opens into the Gulf of Mexico.
The flow in the rivers in the Trinity basin is highly dependent on rainfall. Most of the river flow is rainfall runoff and between rains the flow is therefore often quite. Lack of natural flow in dry periods makes the river vulnerable to pollution since during those periods, a large part of the flow in the river comes from discharge of wastewater.
The basins geographic location can be seen on the following map of Texas:
This whole basin is however too large to be modeled all at once. Therefore, when it came to the modeling part a small segment was selected from the river. The first selection was a segment called West Fork Trinity River Above Bridgeport Reservoir, segment 812. The 303(d) list describes the segment in the following way:
The Nonpoint Source Model (NPSM) in BASINS did however not accept this river reach network; maybe 12 reaches and watersheds are too complicated for the model. NPSM gave no comment on why it did not accept it but gave no output either.
The next choice was a segment south of the first one, Clear Fork Trinity River Above Lake Weatherford, segment 833. The 303(d) list describes the segment 833 in the following way:
The geographic location of this segment 833 can me see on the following map:
The red star at the end of the watershed represents a USGS flow gage station as well as a water quality station. The USGS station has the name: Clear Fork Trinity River Near Aledo, Texas and its identifying number is 08046000. Data are available at the USGS web site for the station for the time span of 08/01/1947 - 10/09/1975.
BASINS
is an abbreviation for Better Assessment Science Integrating Point and
Nonpoint Sources. The U.S. Environmental
Protection Agency's (EPA's) Office
of Water developed the BASINS
system as an environmental analysis system, which could be used for water
quality studies. It integrates point and nonpoint sources by using various
data layers with analysis tools.
The system consists of
The BASINS system includes a database with maps and associated data from a variety of sources, which are necessary for a watershed-based approach of modeling water quality. Firstly there are base cartographic data such as state, county and HUC boundaries that help the user to choose and define a study area. Then there are general environmental background data such as DEMs, Rf1 and Rf3 river reach files, land use and soil information. Environmental monitoring Data include all kinds of measuring stations and associated data, weather stations, water quality stations, USGS flow gage stations etc. Finally there are point source and loading data, i.e. information on the facilities that have permission to discharge into the river, what substances they are discharging and how much.
Within the GIS environment of BASINS there
are a three assessment tools which allow the user to make quick studies
on the whole project area (Target), sub-basins (Assess) or specific facilities
(Data mining).
Target performs a broad-based assessment on the entire project area. It summarizes a large amount of detailed data from all relevant sites to evaluate the mean value of a selected parameter for each watershed and allow the user to estimate visually which watersheds might have problems.
If for example the water quality of the Trinity Basin is targeted and the constituent phosphorus is selected, The result are graphs/maps like the following.
The chart in the upper right corner shows the distribution of how many water quality stations exceed a threshold value (here the value is 0) in a sub-watershed. Down to the left is chart describing how many sub-watersheds fall into each category of concentration level. The most informative map is however up in the left corner; it shows the Trinity Basin divided into sub-watersheds by HUC boundaries. Different colors show difference in mean measured concentration of phosphorus. Obviously there is one sub watershed, which has a larger concentration of phosphorus than the other; this is the basin beneath the Dallas-Fort Worth area.
The Assess option is used to assess data on an individual watershed or a limited set of watersheds. It allows the user to evaluate amount of substance discharged at specific facilities or concentration of constituents measured at monitoring stations within the sub-watershed.
Since one sub-basin stuck out in the context of having large measured values of phosphorus in the preceding use of the tool Target, the Assess tool was used to examine the watershed in more details. In the following graphs/maps the permitted discharges have been assessed with a view of total suspended solid discharged.
The BASINS system also allows the user to make summarizing reports on some key watershed information, either for one or more watersheds. When the report option is chosen, BASINS generates maps and tables from its database to summarize the overall conditions of the watershed. If the Landuse Distribution Report option is for example selected the result will be the following:
These three assessment tools and report generation tool are practical when the user wants to examine the current condition of the watershed, where the troublesome spots are. I.e. where the quality of water is not good enough, and what might be causing the trouble, point or nonpoint sources. These tools can however not forecast what influence changes might have; they can just describe what has been measured. To predict effects of a changed use of land or a new discharging facility on water quality, models have to be set up according to current conditions, they calibrated and improved until they agree with measured data. Only after sufficient calibration can the model be used for evaluation of impacts of alteration of point or nonpoint sources.
There are two Stream Models included in BASINS 2.0, QUAL2E and TOXIROUTE. They are one-dimensional, steady state models that route pollutants down a river and evaluate thereby impacts of point and nonpoint source pollutants on the water quality of a river. In the Arc View based part of BASINS an input file is produced for the selected watershed, and the output can also be viewed in the Arc View built-in visualizer.
QUAL2E is used for simulations of temperature, biochemical oxygen demand and dissolved oxygen, conservative and non-conservative substances. It divides the reaches in several segments of equal length and routes the constituent through each segment; allowing point/nonpoint sources to be added to each of the segments. Important factor when modeling with QUAL2E is to know that the program is not compatible with Windows NT and there is no workaround for the problem.
Therefore after a long time of trying to run the model (on Windows NT) without any kind of output, the non-compatibility was revealed and no further study was done on this model since all computers available had Windows NT.
TOXIROUTE calculates concentrations of general water quality constituents based on dilution and first order decay algorithms. This program will probably not be included in the next edition of BASINS. Therefore, no effort was made to make this program run.
Those two water quality models can however not handle variations with time or calculate nonpoint source pollution, for that task a more complicated model has to be used.
NPSM is the BASINS nonpoint source model. It estimates nonpoint source loading from mixed land uses and integrates it with point source loading for a prediction of concentration of constituents. It can therefore describe how much of the constituents in the river come from surface runoff and how it would change with a different use of land. The Arc View based part of BASINS creates an input file for a selected watershed by using Rf1 as a river network, extracting information on point sources from its database and calculating what percent of the land surface belongs to each land use category.
When the model is done with a successful simulation, the output as well as actual data can be compared in the NPSM-postprocessor for calibration of the model.
Getting a model like NPSM to run might not
always be as easy as the manual implies. The main disadvantage of the NPSM
is probably lack of information, often does the model neither run nor does
it supply the user with any information on why it does not. Hints on where
the model stopped or what parameters were not acceptable are necessary.
Oftentimes does the user have to start all over again with the simplest
type of model and work his/her way by making the model more complicated
step by step and keeping track of all changes that might disturb the model.
Until now only some general flow and water quality parameters have been
simulated since the model fails to work when more complicated parameters
are selected. Results from the simulation will be presented later in this
chapter, they basically show that calibration will be needed before the
model can be used to predict flow or water quality in the river reaches
involved.
 |
A model was built for the aforementioned watershed, Clear Fork Trinity River. An input file was imported from Arc View into NPSM and many options were checked out. Following is a description of a successful building of a model, with respect to getting an output file. |
NPSMs Windows interface has the following buttons.
The buttons work in the following way when using the imported input file from Arc View.
Reach Editor
 |
The input file from Arc View BASINS should have populated all areas within this option. In Add/Remove Reaches the user can erase or add more reaches if necessary and by using the visualization option the reach network can be reviewed and corrected visually. Each reach then has some informative parameters such as reach length, slope and elevation. |
Simulation Time and Meteorological Data
 |
Here a weather station should be chosen with respect to which one has the most representing weather for each of the sub-watersheds. In this project three different weather stations were selected and flow from each of those was compared to measured flow at the USGS flow station at the end of the watershed. Simulation time should also be chosen here within the time span of the weather station. |
Landuse Editor
 |
In the Landuse Editor window the input file should have populated everything. This is a description of how large part og each sub-watershed falls into each land use category. |
Control
Cards
 |
In the Control Card option, parameters that correspond to the constituents you want to model are selected. Here the selected parameters are PWATER, to model the flow, and PQUAL, to model general water quality. This choice was made because of the fact that the program would not run if something else were selected. |
Pollutant
Selection
 |
In the Pollutant
Selection list the pollutants you want modeled for the output have to be
chosen. The user should also be allowed to choose more parameters with
the restriction that the corresponding parameters were chosen in the Control
Card option.
Since only WATER and QUAL parameters were chosen in the Control Cards window only general quality parameters were chosen here. |
Point Sources
 |
Information on all the facilities in the watershed that have permissions to discharge into the river should be within Point Sources. The input file should have populated all the cells here so the user just has to check whether everything seems all right. |
Default Data Assignment
 |
In Default Data Assignment,
the file starter.def was selected, it has parameters, describing each land
use category, a theoretical river and some constituent parameters. The
rivers in the model as well as the land use are assigned the values of
the items in the default file when the Auto Load button is pressed.
This starter.def file came with BASINS, but a more specific file for Texas would probably be a better choice, if it were available. |
Data
Editior
 |
The parameters in the Data Editor were assigned values by the starter.def file but the values of each parameter can be changed here for model improvement. |
Output Manager
 |
In the Output manager you can then select what kind of an output file you want. |
Run button just has to clicked on
View
Time Series Output
 |
When the run button has been pushed, the model will probably produce an output file like the one to the right, which can be viewed in the NPSM Post-processor. |
When all this has been done there is time to compare the results from the simulation to the actual measured data. The comparison is useful to evaluate whether the output is reasonable. It also gives the user an idea on which parameters have to be changed in order to get a model that can predict influences of changes in vegetation as well as point source loading.
The output from the described simulation is as follows:
The USGS flow data from a station at the end of the watershed are here compared to flow calculated by NPSM using three different weather stations. As you can see NPSM does not follow the measured curve well but by calibration of the model, a better flow prediction could be made by NPSM.
Fecal coliform, BOD5 and phosphorus concentration was also simulated here and on the following graphs the results are compared to actual data from the water quality station at the end of the watershed. The results weren’t great but the NPSM results are at least on a similar scale as the actual data.
Those results show how important it is to have actual data to compare the model output with. If no measured data were available the results would seem quite good. The comparison shows however that even though the calculated concentration are on a similar scale as the real data, adjustments have to be made to the model in order to make it a useful tool in a water quality study of the segment.
The BASINS system seems in most ways interesting and easy to use. Installation and setup of the GIS-based part of the system proved to be easy, the Arc View project includes good assessment tools and necessary data for evaluation of current conditions of watersheds. The modeling part however, proved not to be as user friendly as the GIS part. For predictions of what influences changes on land use or point sources two of three models were tried, QUAL2E and NPSM.
Important factor when modeling with QUAL2E is to know that the program is not compatible with Windows NT and there is no workaround for the problem. This fact should be presented in a more obvious way to prevent a Windows NT user from struggling with an impossible task.
The weak side of NPSM is a lack of information, the program should give the user some error messages or instructions when the model can not run due to some mistakes in the input, its frustrating to try over and over again without knowing what is wrong. I did not manage to get the NPSM working except for modeling general water quality and flow parameters, more complicated models did not give an output file. Since the program gave no comments on wrong setup, an improvement or corrections are hard to make.
Texas Natural Resource Conservation Commission, Water Quality Division. 1998. State of Texas 1998 Clean Water Act Section 303(d) List and Schedule for Development of Total Maximum Daily Loads. TNRCC. Austin Texas.
Texas Natural Resource Conservation Commission. (No date). Texas Surface Water Quality- What Is it, and How Is It Measured? [Online]. Available: http://www.tnrcc.state.tx.us/water/quality/tmdl/index.html [1999, May 6].
U.S Environmental Protection Agency. 1999. BASIN, Better Assessment Science Integrating Point and Nonpoint Sources [Online]. Available: http://www.epa.gov/OST/BASINS/ [1999, May 6]
U.S Environmental Protection Agency. 1998. Better Assessment Science Integrating Point and Nonpoint Sources, BASINS Version 2.0, User's Manual. Washington
U.S Environmental Protection Agency. 1999. Technical Note #3 - NPSM/HSPF Simulation Module Matrix. [Online]. Available: http://www.epa.gov/OST/BASINS/bsnsdocs.html [1999, May 5]
U.S. Geological Survey. 1998. Water Resources, Data [Online]. Available: http://water.usgs.gov/data.html [1999, May 6].