What question did this study set out to answer?

The aim is to evaluate hydrological and anthropogenic impacts on water quality in the Wadi Al-Ahsaba watershed.

June 27, 2026Earth0 citationsOpen Access

Hydrogeochemical Controls and Anthropogenic Impacts on Water Quality in an Arid Wadi-Dam System, Saudi Arabia

MBMohammed BenaafiKing Fahd University of Petroleum and Minerals AAAli Q. AlorabiAl Baha University AAAli Y. AlzahraniAl Baha University

Key Points

The aim is to evaluate hydrological and anthropogenic impacts on water quality in the Wadi Al-Ahsaba watershed.
Analyzed 21 water samples (15 surface, 6 groundwater) for general chemistry and major ions.
Utilized hydrogeochemical analysis and principal component analysis (PCA) to distinguish geogenic and anthropogenic influences.
Evaluated pollution status using water quality index (WQI) and other contamination metrics.
90% of samples exceeded nitrate drinking water standards, with levels ranging from 9.5 to 109 mg/L.
95% of tested samples exceeded TDS drinking water standards, with values between 522 and 1003 mg/L.
WQI values ranged from 43 (excellent) to 134 (poor), indicating varying water quality.

Abstract

The Wadi Al-Ahsaba watershed is an arid to semi-arid catchment situated in southwestern Saudi Arabia, characterized by intermittent surface flow, high evaporation and low rainfall, and a dam reservoir built for flood control. The work aims to assess hydrological and anthropogenic controls on surface and groundwater quality, pollution status, and human health risks using an integrated approach of hydrogeochemical analysis, multivariable statistics, and water quality and contamination indices. A total of 21 water samples (15 surface water, 6 groundwater) were analyzed for general chemistry, major ions, and trace elements. Hydrogeochemical analysis and principal component analysis (PCA) were implemented to differentiate the geogenic from anthropogenic control on water quality. The pollution status and associated risk were evaluated using water quality index (WQI), contamination degree (Cd), Hazard Quotient (HQ), and Hazard Index (HI). Results suggest limited surface–groundwater interaction, with surface water dominated by Ca–Mg–HCO3 facies, indicating recent recharge and limited water–rock interaction, whereas groundwater exhibits mixed Ca–Mg–Cl and Ca–Na–Cl–SO4 types, revealing longer residence time and water–rock interaction. Nitrate (9.5–109 mg/L) and TDS (522–1003 mg/L) exceeded drinking water standards in 90% and 95% of tested samples, respectively, and WQI ranged from 43 to 134, reflecting excellent to poor water. High non-carcinogenic risk from nitrate was observed, especially for infants. The study concluded that the geogenic processes (water–rock interaction, evaporation, and mineral dissolution) control the general chemistry of tested water, while anthropogenic input from wastewater and agriculture input are likely contributors to nitrate contamination. The study contributes to the understanding of arid wadi-dam systems by revealing how limited recharge, hydrological connectivity, and episodic flow control contaminant transport and persistence, underscoring the critical role of integrated hydrological analysis and land use management in safeguarding freshwater resources in arid environments.

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