Abstract
Abstract. Optimum management of irrigated crops in regions with shallow saline groundwater requires a careful balance between application of irrigation water and upward movement of salinity from the groundwater. Few field-validated surrogate models are available to aid in the management of irrigation water under shallow groundwater conditions. The objective of this research is to develop a model that can aid in the management using a minimum of input data that are field validated. In this paper a 2-year field experiment was carried out in the Hetao irrigation district in Inner Mongolia, China, and a physically based integrated surrogate model for arid irrigated areas with shallow groundwater was developed and validated with the collected field data. The integrated model that links crop growth with available water and salinity in the vadose zone is called Evaluation of the Performance of Irrigated Crops and Soils (EPICS). EPICS recognizes that field capacity is reached when the matric potential is equal to the height above the groundwater table and thus not by a limiting hydraulic conductivity. In the field experiment, soil moisture contents and soil salt conductivity at five depths in the top 100 cm, groundwater depth, crop height, and leaf area index were measured in 2017 and 2018. The field results were used for calibration and validation of EPICS. Simulated and observed data fitted generally well during both calibration and validation. The EPICS model that can predict crop growth, soil water, groundwater depth, and soil salinity can aid in optimizing water management in irrigation districts with shallow aquifers.
Highlights
Irrigation water is a scarce resource, especially in arid and semi-arid areas of the world
We presented a surrogate model for the vadose zone with shallow groundwater using the novel concept that the moisture content at field capacity is a unique function of the groundwater depth after irrigation or precipitation that wets up the entire soil profile
In the EPICS model, the soil profile is divided into five layers of 20 cm and a sixth layer that stretches from the 100 cm depth to the water table below (Fig. 1)
Summary
Irrigation water is a scarce resource, especially in arid and semi-arid areas of the world. In arid and semi-arid areas where people divert surface water for flood irrigation and have poor drainage infrastructures, the groundwater table is close to the surface because more water has been applied than crop evapotranspiration. We presented a surrogate model for the vadose zone with shallow groundwater using the novel concept that the moisture content at field capacity is a unique function of the groundwater depth after irrigation or precipitation that wets up the entire soil profile. To make the Shallow Vadose Groundwater model more physically realistic, we added a crop growth model and included the effect of salinity and moisture content on evaporation and transpiration directly in this study. On days without water input at the soil surface, an upward groundwater flux U (j , h, t) and salt S(j , t) are considered. Transpiration, T (j , t), removes water from the layers with roots of the crops and evaporation, E(j , t), from all layers
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