MODELING EFFECTS OF BRUSH MANAGEMENT ON THE RANGELAND WATER BUDGET: EDWARDS PLATEAU, TEXAS 1

The Soil and Water Assessment Tool (SWAT) was used to evaluate the influence of woody plants on water budgets of semi- arid rangelands in karst terrain. The model was configured for the hydrologic evaluation of the North Fork of the Upper Guadalupe River watershed and was calibrated and verified using measured flow data. Nash and Sutcliffe fit efficiencies for daily and monthly verification periods were 0.09 and 0.50, respectively. Streamflow, baseflow, and evapotranspiration (ET) rates were comparable to published field data. Simulated deep recharge was considerably higher than the published values for the Edwards Plateau. The model was then used to simulate conditions with existing brush cover and four different brush removal scenarios. Scenarios were created to represent existing brush and the removal of brush from only locations that were either covered by heavy brush, were on a moderate slope, or were in shallow soils. Resulting data was com- pared to previous studies of both field experiments and model simu- lations. Maximum brush removal resulted in a reduction in ET equal to 31.94 mm/yr depth over the entire basin, or 46.62 mm/yr depth over the treated area. Removal of heavy brush cover resulted in the greatest changes in evapotranspiration, surface runoff, base- flow, and deep recharge. Slope was found to have the greatest effect on lateral subsurface flow. (KEY TERMS: evapotranspiration; water budget; range hydrology; brush management; Edwards Plateau; SWAT.)

[1]  Gilbert T. Bernhardt,et al.  A comprehensive surface-groundwater flow model , 1993 .

[2]  J. Arnold,et al.  AUTOMATED METHODS FOR ESTIMATING BASEFLOW AND GROUND WATER RECHARGE FROM STREAMFLOW RECORDS 1 , 1999 .

[3]  J. G. Arnold,et al.  PREDICTING SEDIMENT AND PHOSPHORUS LOADS IN THE ROCK RIVER BASIN USING SWAT , 2000 .

[4]  H. Mayeux,et al.  Evaporation from rangeland with and without honey mesquite. , 1991 .

[5]  O. V. Auken.  Shrub Invasions of North American Semiarid Grasslands , 2000 .

[6]  Ralph A. Wurbs,et al.  Scale-dependent soil and climate variability effects on watershed water balance of the SWAT model , 2002 .

[7]  D. N. Ueckert,et al.  Redberry juniper-herbaceous understory interactions. , 1995 .

[8]  David R. Maidment,et al.  Spatial Water Balance in Texas , 1994 .

[9]  W. H. Blackburn,et al.  Rainfall interception by midgrass, shortgrass, and live oak mottes. , 1987 .

[10]  John R. Williams,et al.  A modeling approach to determining the relationship between erosion and soil productivity [EPIC, Erosion-Productivity Impact Calculator, mathematical models] , 1984 .

[11]  Jason D. Afinowicz,et al.  A Process for Assessing Wooded Plant Cover by Remote Sensing , 2005 .

[12]  T. Raines,et al.  Simulation of Flow and Effects of Best- Management Practices in the Upper Seco Creek Basin, South-Central Texas, 1991-98 , 2002 .

[13]  S. Archer,et al.  Have Southern Texas Savannas Been Converted to Woodlands in Recent History? , 1989, The American Naturalist.

[14]  D. Ockerman.  Simulation of runoff and recharge and estimation of constituent loads in runoff, Edwards aquifer recharge zone (outcrop) and catchment area, Bexar County, Texas, 1997-2000 , 2002 .

[15]  W. Dugas,et al.  Effect of removal of Juniperus ashei on evapotranspiration and runoff in the Seco Creek Watershed , 1998 .

[16]  R. Scott,et al.  ECOHYDROLOGICAL IMPLICATIONS OF WOODY PLANT ENCROACHMENT , 2005 .

[17]  J. Nash,et al.  River flow forecasting through conceptual models part I — A discussion of principles☆ , 1970 .

[18]  Jeffrey G. Arnold,et al.  APPLICATION OF SWAT FOR THE UPPER NORTH BOSQUE RIVER WATERSHED , 2000 .

[19]  James A. Young,et al.  Stem Flow on Western Juniper (Juniperus occidentalis) Trees , 1984, Weed Science.

[20]  Robert C. Maggio,et al.  Autogenic succession in a subtropical savanna: conversion of grassland to thorn woodland , 1988 .

[21]  John R. Williams,et al.  LARGE AREA HYDROLOGIC MODELING AND ASSESSMENT PART I: MODEL DEVELOPMENT 1 , 1998 .

[22]  A. R. Hibbert.  Water Yield Improvement Potential by Vegetation Management on Western Rangelands , 1983 .

[23]  Stephen R. Workman,et al.  SIMULATION OF DAILY AND MONTHLY STREAM DISCHARGE FROM SMALL WATERSHEDS USING THE SWAT MODEL , 2000 .

[24]  B. Wilcox.  Shrub control and streamflow on rangelands: a process based viewpoint. , 2002 .

[25]  H. Wright,et al.  Effect of Prescribed Burning on Sediment, Water Yield, and Water Quality from Dozed Juniper Lands in Central Texas , 1976 .

[26]  Vegetation and water yield dynamics in an Edwards Plateau watershed , 2001 .

[27]  Sung-Min Cho,et al.  SENSITIVITY CONSIDERATIONS WHEN MODELING HYDROLOGIC PROCESSES WITH DIGITAL ELEVATION MODEL 1 , 2001 .

[28]  W. Dugas,et al.  ESTIMATING ASHE JUNIPER LEAF AREA FROM TREE AND STEM CHARACTERISTICS , 1998 .

[29]  E. L. Kuniansky,et al.  Simulations of flow in the Edwards-Trinity aquifer system and contiguous hydraulically connected units, west-central Texas , 1994 .

[30]  P. Ciais,et al.  Consistent Land- and Atmosphere-Based U.S. Carbon Sink Estimates , 2001, Science.

[31]  M. Owens.  The role of leaf and canopy‐level gas exchange in the replacement of Quercus virginiana (Fagaceae) by Juniperus ashei (Cupressaceae) in semiarid savannas , 1996 .

[32]  Keith Beven,et al.  Dalton Medal Lecture: How far can we go in distributed hydrological modelling? , 2001 .

[33]  Peter M. Allen,et al.  Automated Base Flow Separation and Recession Analysis Techniques , 1995 .