Multivariate indications between environment and ground water recharge in a sedimentary drainage basin in northwestern China

Abstract

A paucity of studies on the interaction between environment and ground water recharge severely restricts the ability of people to assess future water resources under changing environment. In this study, an effort to explore the relationship between the arid environment and ground water recharge was carried out using multivariate statistical techniques in a sedimentary drainage basin (the Jungar) in northwestern China. Hierarchical cluster analysis (HCA) and principal components analysis (PCA) were performed based on hydrogeochemical data to assess the ground water recharge and its governing factors. Observation of the HCA and PCA analytical results revealed a division of seven clusters (C1 to C7) and three principal components (PC1 to PC3), which explained 59.6%, 16.6% and 10.9% of the variance, respectively, and thus, accounted for the majority of the total variance in the original dataset. Based on these Q-mode HCA clusters and R-mode PAC scores, dominant environmental processes influencing recharge regimes were identified, i.e., geogenic, geomorphoclimatic, and anthropogenic, which separated the recharge regimes into four zones (Zone I to Zone IV). Zones I and II (C4+C1) were associated to “elevated hydroclimate degree” coupled to “low salinity”. Zone III (C2+C3) was associated to “moderately elevated salinity” and evidently “elevated contamination” but coupled to “low hydroclimate degree”. Zone IV (C5+C6+C7) was associated mainly to “elevated salinity” coupled to “low or inverse hydroclimate degree”. It revealed that the geogenic processes are more significant (60%) than the geomorphoclimatic (17%) and anthropogenic (11%) processes. As a result, the overall recharge process is rather heterogeneous and is strongly environment dominated in the Jungar drainage system. Compared with other watersheds in arid environment, a distinctive feature of the Jungar waters is that they are affected by a combination of natural and non-natural events, rather than following a steady and continuous geological evolution. These will continue to influence the recharge regime of the Jungar for a long time due to its steady tectonics and arid climate. However, changing rainfall, but not snow, is becoming the key factor driving changes in ground water resources in this drainage system, as results of the decades of warming and humidification in northwestern China.