Abstract
Water storage in unsaturated and saturated zones during the crop non-growing season is one of the important supplementary water resources to meet crop water requirements in arid areas with shallow water table depth. It is necessary to analyze utilization of the soil-ground water storage during the crop growing season and its attribution to irrigation during the non-growing season. To facilitate the analysis, a new method based on measurements of soil moisture content and water table depth is developed. The measurements used in this study include (1) 15-year data of soil moisture content within a depth of 1 m from the land surface and water table depth measured in Jiefangzha, including its four subareas and (2) 4-year data of the same kind in Yonglian, located in arid northern China. The soil-ground water storage utilization is calculated as the difference of water storage between the beginning and end of the crop growing season in the whole computational soil profile. The results of average soil-ground water storage utilization in Jiefangzha and its four subareas and Yonglian are 121 mm, 126 mm, 113 mm, 124 mm, 185 mm and 117 mm, and the corresponding average utilization efficiencies in the non-growing season are 32.2%, 32.5%, 31.5%, 31.6%, 57.3% and 47.6%, respectively. Further, the water table fluctuation method was used to estimate the variation in water storage. The coefficients of soil-ground water storage utilization, soil-ground water storage utilization below 1 m soil depth and ground water utilization are defined, and their average values are 0.271, 0.111 and 0.026 in Jiefangzha, respectively. Then, the contribution of soil-ground water storage utilization to actual evapotranspiration is evaluated, which are over 23.5% in Jiefangzha and Yonglian. These results indicate that the soil-ground water storage plays an important role in the ecological environment in arid areas with shallow water table depth.
Highlights
Agricultural irrigation has consumed the largest amount of fresh water in most countries over recent decades due to the rapid increase in agricultural areas [1], which may aggravate water resources scarcity and lead to a challenge for socio-economic development [2], especially in arid regions [3].Water consumed by plants is supplied by irrigation water, and by water storage in the unsaturated and saturated zones in arid areas with shallow water table depth [4,5]
The contributions of soil-ground water storage storage utilization, soil‐ground water storage utilization below 1 m soil depth and ground water utilization, soil-ground water storage utilization below 1 m soil depth and ground water utilization to utilization to actual evapotranspiration are further evaluated
(2) More than 30% of the autumn irrigation water during the non‐growing season can be used as soil‐ground water utilization in arid areas with shallow water table depth
Summary
Agricultural irrigation has consumed the largest amount of fresh water in most countries over recent decades due to the rapid increase in agricultural areas [1], which may aggravate water resources scarcity and lead to a challenge for socio-economic development [2], especially in arid regions [3].Water consumed by plants is supplied by irrigation water, and by water storage in the unsaturated and saturated zones in arid areas with shallow water table depth [4,5]. There are plans to decrease the amount of autumn irrigation water, due to the shortage of surface water resources of the Yellow river [9]. Estimating the soil-ground water storage utilization in the autumn irrigation (non-growing season) is of significant importance for adjusting a suitable irrigation quota during the crop growing season and maintaining crop production in this area. What is more, analyzing the influence mechanism of the impact factors (including the autumn irrigation scheme and planting structure) on soil-ground water storage utilization is useful for water management in arid areas with shallow water table depth.
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