| This study presents a tool for community-based water resources management in hillside watersheds. A simulation-based methodology was developed for assessing water scarcity on a watershed scale. The Spatial Water Budget Model was developed for simulating water supply and demand and analyzing temporal and spatial variations in overall water balance and in stream water flow due to changes in land use, population and industrial development.; Daily domestic, industrial, and agricultural water demands for the period 1994--1997 were quantified for the Cabuyal River watershed in southwest Colombia. Simulated flow rates in the river compared well to measured flow rates and varied considerably over space and time. The 4-year average annual simulated flow rate was 824 L/s, but it dropped below 300 L/s in the dry season and more than doubled during periods of heavy rainfall. Base flow contributed more to river flow in the upper part of the watershed than in the lower part, 86.7% and 75.9% respectively, due to differences in land use. Although simulated water availability was at its lowest during periods when water was needed most, the river still supplied sufficient water to meet all water demands on any day from 1994 through 1997.; Three different scenarios and their implications on water scarcity in the Cabuyal River watershed in the year 2025 were analyzed: Corporate Farming, Ecological Watershed, and Business as Usual. Different land use, water demand, demographics, and presence of dams characterized each scenario. A plausible land use pattern for each scenario was created with a rule-based land use change model. The percentage of the area covered by each land use type was significantly different for each scenario.; Simulation results suggested that the watershed has the potential to meet anticipated increases in water use under all three scenarios, although up to 61% of the river flow was used in the dry season under the Corporate Farming scenario if there were no dams. Current water management practices in the watershed do not provide much leeway for increased water use. Simulation results indicated specific water management measures that could be taken. For example, dams with a volume of about 0.5--1 million m3 could be built to supply enough irrigation water and maintain flow rates of 350 L/s. Because of their limited capacity, current drinking water systems should be used for domestic purposes exclusively. |
