River Water Quality and Quantity Determinants in a Developing Country

Abstract

Developing countries rely to a large extent on international donors to improve water security. Yet, international interventions often end up with low efficiency impacts because of the lack of a priori comprehensive projections. With this in mind, this paper presents a scenario-based methodology to forecast river water quantity and quality in a common multi-stressor situation, that is combined impact of climate change, population growth and wastewater discharge. As an illustrative case, El Kalb River basin, in Lebanon, was simulated under four scenarios up to year 2050, using Water Evaluation and Planning (WEAP) model. The observed trends indicate that mean annual streamflow and flow to groundwater could decrease by around 10 to 23% each due to climate change, while water demand is expected to increase by 16 to 32%. As to water quality, the maximum BOD of 68 mg/L (in 2019) can be decreased by introducing wastewater treatment (starting 2021 as planned by national authorities) to 44 mg/L, only to increase again to 63 mg/L in 2050 due to population growth. Considering climate change, water quality is expected to deteriorate further and the maximum BOD would reach 118 mg/L and 147 mg/L in 2050 under RCP 4.5 and RCP 8.5 scenarios, respectively. Even though the planned wastewater treatment facilities would reduce BOD by 34%, it was shown that the river would never meet water standards – under any of the proposed scenarios. The approach adopted in this paper is recommended for quantification of the efficiency of river protection plans in developing areas.