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In cooperation with the Texas State Soil and Water Conservation Board and
U.S. Department of Agriculture, Natural Resources Conservation Service

Simulation of Flow and Effects of Best-Management Practices in the Upper Seco Creek Basin, South-Central Texas, 1991–98

By David S. Brown and Timothy H. Raines

U.S. Geological Survey
Water-Resources Investigations Report 02–4249

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Purpose and Scope

Description of Study Area

Description of Simulation Model


Simulation of Flow

Model Setup

Model Calibration and Testing

Error Analysis

Sensitivity Analysis

Simulation of Best-Management Practices

Brush Management

Weather Modification




1–4.   Maps showing:
  1.   Location of the upper Seco Creek Basin, south-central Texas
  2.   Data-collection network in the upper Seco Creek Basin
  3.   Land use/cover in the upper Seco Creek Basin
  4.   Surface and shallow subsurface geology in the upper Seco Creek Basin
5–10.   Graphs showing simulated and observed flow for:
  5.   08201500 Seco Creek at Miller Ranch near Utopia
  6.   08202450 Seco Creek Reservoir Inflow near Utopia
  7.   08202490 Seco Creek Reservoir Outflow near Utopia
  8.   08202700 Seco Creek at Rowe Ranch near D’Hanis
  9.   08202790 Parkers Creek Reservoir Inflow near D’Hanis
  10.   08202810 Parkers Creek Reservoir Outflow near D’Hanis
11.   Graphs showing difference between simulated and observed monthly discharge for upper Seco Creek subbasins


1.   Daily rainfall, streamflow, and reservoir-content stations in the upper Seco Creek Basin
2.   Process-related model parameters for the Hydrological Simulation Program—FORTRAN
3.   Basin-related model parameters for the Hydrological Simulation Program—FORTRAN
4.   Basin-related parameters for each gaged subbasin of the upper Seco Creek Basin
5.   Calibration annual parameters
6.   Calibration monthly parameter
7.   Initial-condition values for model calibration
8.   Summary of calibration and testing results for upper Seco Creek subbasins
9.   Summary of calibration and testing errors for upper Seco Creek subbasins
10.   Simulation results from a 5- to 6-percent reduction in evapotranspiration associated with brush management
11.   Simulation results from a 10-percent increase in rainfall totals and intensities associated with weather modification


The Hydrological Simulation Program—FORTRAN model was used to assess the effects of two best-management practices—brush management (removal of woody species locally known as cedar) and weather modification (rainfall enhancement)—on selected hydrologic processes in six subbasins that compose the upper Seco Creek Basin in south-central Texas. A parameter set for use with the model was developed to simulate surface-water-budget components for the six gaged subbasins.

Simulation of brush management, represented by decreases in simulated evapotranspiration of 5 to 6 percent, resulted in increases of 1 to 47 percent in annual runoff and increases of 14 to 48 percent in surface runoff for the six subbasins. Simulation of weather modification, represented by a 10-percent increase in rainfall totals and intensities, resulted in increases of 5 to 6 percent in evapotranspiration, increases of 2 to 92 percent in annual runoff, and increases of 36 to 101 percent in surface runoff.

Rainfall and runoff data for the study were collected during January 1, 1991–September 30, 1998. Data from 60 storms were used for the simulations. The model was calibrated with data from 33 storms (in two subbasins) and tested with data from 27 storms (in four subbasins). Twenty-one pervious land segments were defined for the study on the basis of geology and land cover. An error analysis and a sensitivity analysis were done on each subbasin, and the results were used to develop the final parameter set.


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