Vulnerability of the Metropolitan District of Quito’s Water Resources in the face of Climatic and Anthropogenic Uncertainties

Abstract:

Earlier this year the Stockholm Environment Institute (SEI) concluded a vulnerability analysis for the Metropolitan District of Quito (DMQ) in Ecuador. Vulnerability assessments were done for five sectors in the region: water resources, public health, agriculture, ecosystems and forest fires. This abstract focuses specifically on the vulnerability of the DMQ’s water resources to climatic and anthropogenic uncertainties.

This analysis focused on vulnerability of potable water supply for the city of Quito, as well as industrial and agricultural water needs. Current and future vulnerability was assessed in the face of a number of scenarios of climatic and non-climatic uncertainties. The assessment used an integrated water resources model developed by Quito’s National Polytechnic University for the surrounding Guayllabamba river basin. The model was built using the Water Evaluation and Planning (WEAP) software, and encompasses the urban, rural/agricultural, and industrial demands throughout the basin, linking them with existing surface and ground-water supplies.

Five future scenarios were constructed in the WEAP basin model out the year 2050 in order to assess their effects:

• Urban population growth (~70% by 2050).
• Urban population growth + rising mean air temperatures (~+2°C by 2050).
• Urban population growth + rising temperatures + drought (recurring 3-year drought cycles built into the projection) 
• Urban population growth + rising temperatures + conversion of ‘paramo’ alpine tundra ecosystem into cultivated land. (WEAP allows the user to define various types of land cover extent throughout the basin, along with their unique physical characteristics to simulate rainfall-runoff. Conversion of ‘paramo’ land cover to agriculture was evaluated to see potential effects it may have on the system's hydrology)
• Urban population growth + rising temperatures + drought + conversion of ‘paramos’

Coverage of demands in the model was used as the primary vulnerability metric, with urban demands experiencing supply shortages of up to 20-25% under the most stressful scenarios, a shortage which is dampened by significantly increased groundwater pumping. Rural and industrial demands suffer much more severe shortages, with nearly all demands going unmet in a number of scenarios.