Modelling groundwater recharge and discharge in Hetao irrigation district using water balance model

Abstract

【Background and Objective】 Irrigation in the Hetao irrigation district relies on water diversion from the Yellow River. However, its flat terrain coupled with suboptimal irrigation and drainage practices over the past decades has resulted in groundwater table rise, leading to significant soil salinization. This paper develops a water balance model to calculate groundwater recharge and drainage in the irrigation district. 【Method】 A comprehensive water balance model was established by accounting for seasonal freezing and thawing, as well as groundwater drainage. It was then applied to the Yichang area in the irrigation district. Sensitivity of the model was analyzed using the Latin Hypercube-One-At-a-Time (LH-OAT) method; parameters in the model were estimated using the ensemble square-root method of data assimilation (ES-MDA). 【Result】 Sensitivity analysis reveals that change in groundwater depth is sensitive to parameters including the critical depth of phreatic groundwater table below which groundwater evaporation ceases, coefficient of phreatic groundwater evaporation and coefficient of irrigation water recharge. The model accurately reproduces the variation in groundwater depth and groundwater drainage in the studied area. Groundwater recharge primarily emanates from irrigation water infiltration, while drainage is predominantly through groundwater evaporation. The analysis identifies seasonal fluctuations in groundwater storage, which is influenced by factors such as irrigation water diversion, groundwater depth and groundwater drainage rate. 【Conclusion】 The proposed water balance model accounts for freezing and thawing, as well as groundwater discharge. Practical application shows the model is robust for modelling groundwater dynamics in the Yichang area in the Hetao irrigation district. Monthly change in groundwater storage is influenced intractably by irrigation practices, groundwater dynamics and climatic condition.

Keywords

• groundwater
• water balance model
• recharge
• discharge
• hetao irrigation district