Assessing the Influences of Land Use Change on Groundwater Hydrochemistry in an Oasis-Desert Region of Central Asia

Abstract

Land use change greatly affects groundwater hydrochemical cycling and thereby food and ecosystem security in arid regions. Spatiotemporal distribution of groundwater hydrochemistry is vital to understand groundwater water-salt migration processes in the context of land use change, while it is not well known in the oasis-desert region of arid inland basins. Here, to investigate the influences of land use change on groundwater hydrochemistry and suggest sustainable management, 67 water samples were obtained in the Luntai Oasis, a typical oasis desert of Central Asia. Stable isotopes and chemical components of samples were analyzed. Piper and Gibbs plots were used to elaborate the chemical type and major mechanisms controlling water chemistry, respectively. The results showed that cultivated land area has markedly expanded in the Luntai Oasis over the last 20 years (increasing by 121.8%). Groundwater seasonal dynamics and groundwater–surface water interaction were altered dramatically by farmland expansion and groundwater exploitation. Specifically, the spatial heterogeneity and seasonal variability of groundwater hydrochemistry were significant. Compared with the desert area, the δ18O and TDS of river water and shallow groundwater in the oasis cropland exhibited lower values but greater seasonal variation. Higher TDS was observed in autumn for river water, and in spring for shallow groundwater. The chemical evolution of phreatic water was mainly controlled by the evaporation-crystallization process and rock dominance, with a chemical type of Cl-SO4-Na-Mg. Significant spatiotemporal heterogeneity of groundwater hydrochemistry demonstrated the influence of climatic, hydrogeological, land use, and anthropogenic conditions. Groundwater overexploitation would cause phreatic water leakage into confined water, promoting groundwater quality deterioration due to fresh saltwater mixing. Improving agricultural drainage ditches in conjunction with restricting farmland expansion and groundwater extraction is an effective way to alleviate groundwater environment deterioration and maintain oasis-desert ecosystems in arid regions.

Hydrodynamic Behaviors and Geochemical Evolution of Groundwater for Irrigation in Yaoba Oasis, China

“…Human factors that influence hydrochemical processes are mainly related to the types and intensities of human activities [58]. Excessive groundwater exploitation has resulted in the continuous drop of groundwater level in the oasis [59].…”

Groundwater Hydrochemistry and Recharge Process Impacted by Human Activities in an Oasis–Desert in Central Asia

“…δ 18 O values of middle groundwater had a markable range of −11.24‰ to −7.69‰, with an arithmetic mean value of −9.07‰. Evidently, the δ 18 O value of the middle groundwater ranged between the shallow groundwater and deep groundwater, indicating the recharge of upper phreatic water to confined water [34]. However, δ 2 H and δ 18 O values of deep groundwater differed significantly from other water components, which exhibited small fluctuations.…”

“…Our study area was a piedmont plain, and the lithology of geological strata was primarily overlaid with quaternary unconsolidated sediments. The sediments comprised pebbly sandstone, pebbly gravel, silty fine sandstone and interstratified fine sandstone in the vertical profiles, and sandstone was the dominant rock type [34]. Soil particle size primarily comprised fine sand and medium-fine sand, and the aquifer structure was loose, with strong hydraulic conductivity [35].…”

“…Grassland was the second most dominant land cover type (16.3% in 2021), followed by cultivated land (9.6% in 2021) and forest (5.3% in 2021). The marked increase in cultivated land area in the last few decades (7.1% for 2000 and 9.6% for 2021) resulted in a high water demand for agricultural irrigation [34].…”

Prioritizing Water Resources for Conservation in a Land of Water Crisis: The Case of Protected Areas of Iran

“…However, many important characteristics of water regimes, such as channel morphology, water extraction, and flood control, have suffered from structural and functional ecological disturbance [6,7]. Thus, the sustainable management of inland aquatic ecosystems, particularly streams, directly impacts human well-being [8].…”