Insights into groundwater salinization from hydrogeochemical and isotopic evidence in an arid inland basin

Abstract

In the Manas River basin (MRB), groundwater salinization has become a major concern, impeding groundwater use considerably. Isotopic and hydrogeochemical characteristics of 73 groundwater and 11 surface water samples from the basin were analysed to determine the salinization process and potential sources of salinity.Groundwater salinity ranged from 0.2 to 11.91 g/L, and high salinities were generally located in the discharge area, arable land irrigated by groundwater, and depression cone area. The quantitative contributions of the evaporation effect were calculated, and the various groundwater contributions of transpiration, mineral dissolution, and agricultural irrigation were identified using hydrogeochemical diagrams and δD and δ 18 O compositions of the groundwater and surface water samples. The average evaporation contribution ratios to salinity were 5.87% and 32.7% in groundwater and surface water, respectively. From the piedmont plain to the desert plain, the average groundwater loss by evaporation increased from 7% to 29%. However, the increases in salinity by evaporation were small according to the deuterium excess signals. Mineral dissolution, transpiration, and agricultural irrigation activities were the major causes of groundwater salinization. Isotopic information revealed that river leakage quickly infiltrated into aquifers in the piedmont area with weak evaporation effects. The recharge water interacted with the sediments and dissolved minerals and subsequently increased the salinity along the flow path. In the irrigation land, shallow groundwater salinity and Cl − concentrations increased but not δ 18 O, suggesting that both the leaching of soil salts due to irrigation and transpiration effect dominated in controlling the hydrogeochemistry. Depleted δ 18 O and high Cl − concentrations in the middle and deep groundwater revealed the combined effects of mixing with paleo-water and mineral dissolution with a long residence time. These results could contribute to the management of groundwater sources and future utilization programs in the MRB and similar areas.

Responding to salinity in a rural African alluvial valley aquifer system: To boldly go beyond the world of hand-pumped groundwater supply?

“…In the USA, increasing efforts are now made to delineate brackish groundwater resources to strategically deploy desalination systems there to augment drinking-water supplies as freshwater sources become increasingly scarce (Chowdhury et al, 2018). Groundwater salinity is of mounting concern in many semi-arid systems globally (Boukhari et al, 2018;Liu et al, 2018), and may be increasingly exacerbated by the impacts of irrigated agriculture (Foster et al, 2018). Salinity within shallow or intermediate depth groundwater is considered high over 16% of the global land area, within which some 1.1 billion people reside (Van Weert et al, 2009).…”

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

“…water, due to strong evaporation in arid areas [33]. Furthermore, the mean isotopes of shallow groundwater (δ 18 O = −8.2‰) were lower than the values of river water but higher than those for the middle groundwater (mean δ 18 O = −9.1‰) and deep groundwater (mean δ 18 O = −9.3‰) in the study area.…”

“…This indicated that river discharge was dominated by precipitation during the wet season [38]. Stable isotopes of reservoir water (mean δ 18 O = −6.1‰) were higher than those of river water, due to strong evaporation in arid areas [33]. Furthermore, the mean isotopes of shallow groundwater (δ 18 O = −8.2‰) were lower than the values of river water but higher than those for the middle groundwater (mean δ 18 O = −9.1‰) and deep groundwater (mean δ 18 O = −9.3‰) in the study area.…”

“…Meanwhile, groundwater hydrochemistry could be controlled by the coupling of multiple mechanisms, including evaporation-condensation, leaching and dissolution, precipitation, flushing and mixing, ion exchange, and subsurface biological activity [22,26,31,32]. Additionally, researchers found that spatiotemporal patterns of ion contents in groundwater can provide an insight into the salt origin, evolution, and migration pathways within the aquifers [26,33], which is helpful to understand groundwater water-salt migration in arid areas [34,35]. Yet, alteration of groundwater water-salt circulation by land use change and its influence on groundwater hydrochemistry evolution in the long term are not well known in the oasis-desert region of the Tarim Basin, particularly under the impact of cultivated area expansion.…”

Using bromide data tracer and HYDRUS‐1D to estimate groundwater recharge and evapotranspiration under film‐mulched drip irrigation in an arid Inland Basin, Northwest China

“…The elevation of the basin descends from 5243 m above sea level (a.s.l.) in the mountains to 256 m in the plains (Cheng et al, 2006; Liu et al, 2018).…”