Hydrologic modeling in semi-arid agricultural region: An integrated approach to study water resources in southern San Joaquin Valley, California.

摘要

Drought is one of the most severe natural hazards in the world. This research aims at assessing the limited water resources for better crop-water irrigation and conservation of a drought affected agricultural area in California.;Evapotranspiration (ET) is one of the most important parameters to study crop water use for irrigation scheduling and water management. The remote sensing based ET estimation using Surface Energy Balance Algorithm for Land (SEBAL) is the efficient way to understand crop water use. Crop Water Stress Index (CWSI) quantifies plant stress under different field conditions. The remote sensing approach allows efficient irrigation by applying water when symptoms of water stress appear. To avoid water stress and poor productivity, agriculture relies heavily on surface-water diversions and groundwater extraction. The flow of percolated irrigated water and identification of potential recharge area in the field can minimize the water stress. A thorough understanding of the ET processes and reliable estimates of ET as well as precipitation are required to obtain reliable estimates for water balance.;Results show that the average actual evapotranspiration (ETa) estimated from SEBAL, and Penman-Monteith (PM) was 0.67 mm/h and 0.75 mm/h respectively, with a mean percent difference of 0.109%. The analysis shows that the CWSI when greater than 0.5 resulted in maximum stress whereas the well-irrigated almond crops have CWSI less than 0.24. The flow of groundwater can indirectly influence the status of water stress and ET. It was observed that the groundwater is flowing towards the east of the study area. Excess irrigated water contributes to groundwater recharge. The average Water Surface Elevation (WSE) in 1955 for the growing season (May to July) is 161.04 m. This value is low when compared to those of 2009, 2010, and 2011, which are 237.14 m, 236.28 m, and 235.74 m respectively. The result shows that the average WSE in the wells increased. The total annual deficit in the region is 135.66 +/- 11.3 mm and the total annual surplus is 291.47 +/- 24.29 mm. Irrigation should apply when this region undergoes a period of moisture deficit in the months of May to July. From September to October are months of soil water recharge; from November to early February is the period of water surplus due to winter rainfall. It was observed that the growers should apply a depth of approximately 79.37 +/- 11.3 mm to replenish the soil moisture storage over the entire field in the growing season of almond orchards.