Ten understandings and judgments on water and ecological safety in the Ningxia-Inner Mongolia Hetao Yellow River irrigation district

Zhao Yong; Zhai Jiaqi; Zhang Pengcheng; Liu Kuan; Dong Yiyang; Wang Yanbin; Wang Yong; Yang Zhi; Xu Yang

doi:10.3969/j.issn.1000-1123.2024.23.005

Abstract：The Ningxia-Inner Mongolia Hetao Yellow River irrigation district is a critical ecological security barrier in Northwest China and a core region for green barrier construction and high-quality development.Due to limited rainfall,water diverted from the Yellow River has long been the"lifeline"supporting the economic and social development and ecological security of the area.This study analyzes aspects such as water usage,irrigation efficiency,ecological evolution,groundwater changes,groundwater depth thresholds,autumn and winter irrigation,rice cultivation scale,water-salt balance,and water-saving potential,presenting the following insights:Over the past two decades,the Ningxia-Inner Mongolia Hetao Yellow River irrigation district has been one of the regions with the largest improvements in agricultural water use efficiency.Evaluations of water use efficiency should comprehensively consider regional drought and water scarcity conditions as well as the ecological functions of Yellow River irrigation.Continuous high-intensity water-saving measures have significantly reduced water diversion from the Yellow River,simultaneously decreasing groundwater recharge,leading to widespread and persistent groundwater level declines,which profoundly impact the area's ecological security.Lakes and wetlands have shifted from natural replenishment to predominantly artificial replenishment,and natural vegetation is increasingly transitioning to artificial ecosystems.The study suggests that an average groundwater depth of 2.5 to 3.0 meters is optimal for maintaining ecological health.Although soil salinization in the area shows a general trend of alleviation,it remains in a state of continuous salt accumulation.There is room for optimizing autumn and winter irrigation quotas,though the water-saving potential should not be overestimated.Rice cultivation offers both economic and ecological benefits,but the scale of rice reduction and optimal planting areas require comprehensive evaluation based on practical conditions.Considering economic and technical feasibility and ecological health,the water-saving potential is estimated to be 60 million m3 in the Ningxia Yellow River irrigation district and 220 million m3 in the Inner Mongolia Hetao Yellow River irrigation district.Further water-saving measures would significantly impact the ecology of the irrigation district.This study proposes in-depth water-saving pathways and management strategies under the"defining city,land,population,and production by water"principle,providing a reference for the high-quality development of the Ningxia-Inner Mongolia Hetao Yellow River irrigation district.