Raghuveer K. Vinukollu Class Term Project – GIS in Water Resources November 30, 2004 Determination of Spatially-Distributed Crop Water Requirements at Regional Level using ArcET Utility Raghuveer K. Vinukollu Class Term Project – GIS in Water Resources

Introduction Area: Semi-arid

Introduction Finite water resources Increasing urban and industrial water demand Decreasing agricultural supply

Why GIS ? Point estimate Regional estimate

Objectives Estimate the reference ET values and the crop water requirements generated using ArcET; Etc = ETo x Kc Compare the regional estimates of reference ET values with those generated using soil water balance method; and, Evaluate the reliability of ArcET for practical purposes

ArcET procedure Source: http://hydrology.neng.usu.edu/arcet/

Data Meteorological data -- Monthly precipitation data -- Monthly temperature data Landuse data -- crop distribution in the study area DEM of the study area Site-specific crop coefficients Location and elevation of the meteorological stations

(SCS modified Blanney-Criddle eqn.) Procedure Pre-process Data ArcET Regional ET (Hargreaves eqn.) Regional ET (SCS modified Blanney-Criddle eqn.) ETo - ER Comparison Crop water requirement 50, 75 and 95 % probability for non-exceedence Climatic Scenarios

Discussion Design of new irrigation system Rough estimation Usefulness Design of new irrigation system Rough estimation Interpolation of temperature and precipitation using elevation Limitation Irrigation water management and scheduling Soil water balance

Future work ArcET – More compatible versions file formats ArcET – Soil water balance ArcET – Cell by cell computation of IWR

Acknowledgements Daniele Zaccaria Shujun Li