School of Water and Environment, Chang'an University, No. 126 Yanta Road, Xi'an 710054, Shaanxi, China; Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Chang'an University, No. 126 Yanta Road, Xi'an 710054, Shaanxi, China.
School of Water and Environment, Chang'an University, No. 126 Yanta Road, Xi'an 710054, Shaanxi, China; Key Laboratory of Subsurface Hydrology and Ecological Effect in Arid Region of Ministry of Education, Chang'an University, No. 126 Yanta Road, Xi'an 710054, Shaanxi, China.
Sci Total Environ. 2020 May 15;717:137170. doi: 10.1016/j.scitotenv.2020.137170. Epub 2020 Feb 6.
After a long-term surface irrigation in the southern edge of the Chinese Loess Plateau, the local groundwater is diluted to some extent, which differs from most of the other surface irrigation systems. Identifying the origin of groundwater salinity and determining the implications of irrigation can provide insights into the sustainable development of irrigation systems. In this study, a comprehensive investigation of groundwater, river water, canal water, and irrigation system was conducted. Our results suggest that the irrigation activities produce significant influence on the hydrochemistry of both river and groundwater. In the north-eastern part of the study area, hydrochemistry types are mainly HCO-Na and HCO∙SO-Na types which is recharged by the river replenished by water transfer for irrigation. In the south-western part, groundwater is mainly HCO-Na·Mg type which largely directly receives canal water recharge. The correlation between the irrigation water volume and the salinity variation confirms that mixing with fresh irrigation water which was derived from the reservoirs and the canals, during the irrigation period, dilutes the local groundwater. The natural hydrogeochemical processes of the loess aquifer suggest that the water-rock interactions and cation exchange process supply the excessive Na and other solutes to the groundwater, resulting HCO-Na type water with high salinity. Additionally, the slow Groundwater flow and poor hydrologic cycle between the groundwater and the scarce rainfall promote natural salts accumulation. The δO and δD values indicate that modern rainfall may only account for small part of recharge to groundwater. In contrast, the irrigation water, as well as the canal and the reservoir seepage, contribute to a large proportion of groundwater recharge. The finding is beneficial for the policy-makers for the future water management schemes, in large surface irrigation systems, in order to achieve sustainable development goal.
在中国黄土高原南缘长期进行地面灌溉后，当地地下水在一定程度上被稀释，这与大多数其他地面灌溉系统不同。识别地下水盐度的来源并确定灌溉的影响，可以深入了解灌溉系统的可持续发展。本研究对地下水、河水、运河水和灌溉系统进行了综合调查。结果表明，灌溉活动对河流和地下水的水化学产生了显著影响。在研究区东北部，水化学类型主要为 HCO-Na 和 HCO∙SO-Na 型，由河水补给，河水由灌溉引水补给。在西南部，地下水主要为 HCO-Na·Mg 型，主要直接接受运河水补给。灌溉水量与盐度变化的相关性证实，在灌溉期间，与来自水库和运河的新鲜灌溉水混合，会稀释当地地下水。黄土含水层的天然水文地球化学过程表明，水-岩相互作用和阳离子交换过程为地下水提供了过量的 Na 和其他溶质，导致 HCO-Na 型高矿化度水。此外，地下水与稀少降雨之间缓慢的地下水流动和不良水文循环促进了自然盐分的积累。δO 和 δD 值表明，现代降雨可能只占地下水补给的一小部分。相比之下，灌溉水以及运河和水库渗漏对地下水补给的贡献很大。这一发现有利于未来大面灌溉系统的决策者制定水管理方案，以实现可持续发展目标。
