Rio Seco Basin: Choosing a Water Security Package
The Rio Seco basin is semi-arid and supports 1.2 million people. Upstream, a neighbouring state has built a dam for irrigation; river flow at the border has fallen 35% in ten years. In the city of Rio Seco, the groundwater table has dropped 18 m, and 40% of piped water is unaccounted for, mostly through leaks. Agriculture consumes 70% of the basin’s water, while urban per capita use is 310 litres per day. Three consecutive drought years have reduced reservoir storage to 22%. Proposed solutions are a $600 million desalination plant, a 200 km inter-basin transfer through protected forest, mandatory leak repair, wastewater reuse, and higher agricultural tariffs. The city wants water security within five years.
1. Evaluate which combination of measures would improve water security most effectively within five years.
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The best combination is demand management plus leak repair and wastewater reuse, with desalination as a backup. Leak repair addresses 40% unaccounted-for water-the cheapest supply ‘source’-and would quickly raise available water without new environmental damage. Urban use of 310 litres per day is high, so tariffs and retrofits can cut demand. Wastewater reuse for agriculture or industry frees freshwater, and higher agricultural tariffs encourage efficiency, since agriculture uses 70%. Desalination is reliable but $600 million and energy-intensive; it should be a drought-insurance layer, not the first choice. The inter-basin transfer is expensive, passes through protected forest, and creates ecological and political risk. Within five years, leak repair and reuse can deliver faster, lower-cost gains; desalination can be phased if drought persists.
2. Explain why water scarcity in Rio Seco is partly socially constructed rather than purely physical.
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Water scarcity is partly socially constructed because the basin may have enough water but it is allocated and used inefficiently. The city loses 40% through leaks, and urban demand is 310 litres per day, well above basic needs. Agriculture uses 70%, often for low-value crops, and tariffs may not reflect scarcity. Upstream dam construction has changed physical supply, but the shortage at Rio Seco is amplified by infrastructure neglect, pricing and power relations between upstream and downstream users. The ‘scarcity’ experienced by the city is therefore a product of how water is managed, not simply of rainfall. This matters because supply-side fixes alone would not solve it.
3. Assess the environmental and political issues raised by the proposed inter-basin transfer.
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The 200 km transfer would increase supply but at high cost and environmental risk: construction through protected forest, habitat fragmentation, and altered hydrology. It also creates political dependency on the donor basin, which may face its own drought. Downstream and upstream states may contest the transfer, especially since border flow has already fallen 35%. A defensible position is to treat the transfer as a last resort, require a full environmental assessment and compensation for the forest, and first exhaust leak repair, reuse and demand management. If the donor basin is water-rich and the transfer is seasonal, it could be acceptable; if it transfers scarcity, it is not.