Calibration of a distributed irrigation water management model using remotely sensed evapotranspiration rates and groundwater heads.

摘要

Parameters of the distributed irrigation water management model FRAME are determined by an inverse method using evapotranspiration (ET) rates estimated from the SEBAL remote sensing procedure and in situ measurement of groundwater heads. The model simulates canal and on-farm water management as well as regional groundwater flow. The calibration is achieved in two phases. The data on ET were introduced with the primary intent of improving predictions of ET through better estimated soil hydraulic parameters. During the first phase, soil hydraulic parameters sensitive to ET were optimized. As per the canal running schedule in the study area, the daily values of ET data were synthesized into 16 time periods with 15 periods each of 24 days and one period of 5 days. Use of cumulative (annual basis) ET data results in better estimates of soil hydraulic parameters as compared to temporal (24-day period basis) ET data due to possible errors in other input data. During the second phase of calibration, aquifer drainable porosity and maximum allowable groundwater extraction were optimized against groundwater heads for five years. The calibration was very successful in about 70% of the study area with a coefficient of correlation between simulated and observed groundwater levels of more than 80%. Subsequently the model is validated against groundwater heads for nine years.Digital Object Identifier http://dx.doi.org/10.1002/ird.541