Municipal supply of water under climate variations, growing population, uncertainty, and scarcity, requires water planners to devise feasible and sustainable water sourcing plans; especially for territories relying on groundwater. The conventional ways to cope with water scarcity will no longer guarantee reaping the maximum benefits of declining available water resources. Efficiency and circularity of water are claimed as essential criteria for seeking solutions in designing long-term supply management. A Plan B water assessment applied to a group of municipalities in dry areas of Colombia, is proposed as a hydro-economic model aimed at providing inputs for water resources planning, in which the depletable and common-pool character of aquifers are incorporated. A declination speed index is introduced in two ways: the surface → water table distance and water table → saturated thickness distance. This issue should not be overlooked if spatial differentiation in water tables is incorporated in groundwater extraction permits analysis for multiple and convergent water users. Research results are promising for sustainability of water management in dry areas around the world. Respect to status quo situation a 22% of efficiency gain might be achieved in the next 20 years in Sucre – Colombia, under an efficient model of water consumption. If an efficient and circular water management model is endeavored, multiple gains would be harvested for the benefit of water users and ecosystems relying on aquifers. Increased efficiency is mostly driven by 30 million m3 sewage water recirculated in agriculture, which in turn would prevent aquifer extraction for this activity. In business-as-usual scheme, water efficiency gap will be wider; extraction costs will rise to prohibitive levels for low income municipalities; the declining water tables will oblige to make new punches by simultaneous water users and water declination index calculated would reflect a precipitous decay. Research results provide empirical evidence to the discussion on possible solutions for sustainable and efficient water management as stated in Sustainable Development Goals; specifically target goal 6.4 determines that water efficiency and sustainability in water withdrawals should be accomplished. Local setting on water resources availability, competition on resources, types of users, sewage water treatment technology, energy costs, and institutions in time and place, would determine the replicability of research results.
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