Abstract
Abstract. The temporal and spatial distributions of regional irrigation water productivity (RIWP) are crucial for making decisions related to agriculture, especially in arid irrigated areas with complex cropping patterns. Thus, in this study, we developed a new RIWP model for an irrigated agricultural area with complex cropping patterns. The model couples the irrigation- and drainage-driven soil water and salinity dynamics and shallow groundwater movement in order to quantify the temporal and spatial distributions of the target hydrological and biophysical variables. We divided the study area into 1 km × 1 km hydrological response units (HRUs). In each HRU, we considered four land use types: sunflower fields, wheat fields, maize fields, and uncultivated lands (bare soil). We coupled the regional soil hydrological processes and groundwater flow by taking a weighted average of the water exchange between unsaturated soil and groundwater under different land use types. The RIWP model was calibrated and validated using 8 years of hydrological variables obtained from regional observation sites in a typical arid irrigation area in North China, the Hetao Irrigation District. The model simulated soil moisture and salinity reasonably well as well as groundwater table depths and salinity. However, overestimations of groundwater discharge were detected in both the calibration and validation due to the assumption of well-operated drainage ditch conditions; regional evapotranspiration (ET) was reasonably estimated, whereas ET in the uncultivated area was slightly underestimated in the RIWP model. A sensitivity analysis indicated that the soil evaporation coefficient and the specific yield were the key parameters for the RIWP simulation. The results showed that the RIWP decreased from maize to sunflower to wheat from 2006 to 2013. It was also found that the maximum RIWP was reached when the groundwater table depth was between 2 and 4 m, regardless of the irrigation water depth applied. This implies the importance of groundwater table control on the RIWP. Overall, our distributed RIWP model can effectively simulate the temporal and spatial distribution of the RIWP and provide critical water allocation suggestions for decision-makers.
Highlights
An increasing food demand currently exists due to global population growth, and water resources are limiting food production in many areas (Kijne et al, 2003; Fraiture and Wichelns, 2010)
irrigation water productivity (IWP) is defined as the crop yield per cubic meter of irrigation water supplied, and it is expressed in kilograms per cubic meter (Singh et al, 2004)
Good agreement was obtained by the regional irrigation water productivity (RIWP) model in simulating the IWP and hydrological components during the calibration and validation periods
Summary
An increasing food demand currently exists due to global population growth, and water resources are limiting food production in many areas (Kijne et al, 2003; Fraiture and Wichelns, 2010). In arid and semiarid regions of the world, where irrigated agriculture accounts for about 70 % to 90 % of the total water use (Jiang et al, 2015; Gao et al, 2017; Dubois, 2011), this water deficit and the related land salinity are the two major limitations on agricultural. J. Xue et al.: A novel regional irrigation water productivity model production (Williams, 1999; Xue et al, 2018). The improvement of irrigation water productivity (IWP) is vital (Bessembinder et al, 2005; Surendran et al, 2016). IWP is defined as the crop yield per cubic meter of irrigation water supplied, and it is expressed in kilograms per cubic meter (Singh et al, 2004)
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