Water supply and scarcity – demand, transfers and groundwater
GeographyWater & OceansAges 15–16
Loading…
Sign in to playAn imaginary region with a wet, thinly populated northern basin and a dry southern basin with a coastal city and irrigated farmland. A map shows where water is in surplus or deficit; set rainfall, population, population growth, irrigated area and income level, then build a reservoir, a transfer scheme or a desalination plant, drill more boreholes or save water. Over 30 years the model tracks the water balance, the demand as a share of renewable water, the Falkenmark indicator, physical or economic scarcity, the falling water table, saltwater intrusion, soil salinisation, costs, energy and the effects on rivers.
Lesson: Water resources: supply and demand, physical and economic water scarcity, water management and sustainable supply
What it shows
Water is not always where people need it. In this region the wet uplands have a large surplus, while the dry south, with most of the people and the irrigated fields, is in deficit. Demand rises with population, living standards and irrigation. Supply can be increased with dams, transfers, desalination or more pumping, each with costs, energy use and environmental impacts; or demand can be cut by saving water. Physical scarcity means too little water; economic scarcity means water exists but money, pipes and institutions to deliver it are lacking.
How to use
Set Rainfall, Climate, Income, Population, Population growth and Irrigated land, then press Run to follow 30 years, or use +1 year and +1 drought year. Tick Dam and reservoir, Inter-basin transfer, Desalination, More boreholes or Water saving and compare the water balance graph, water table, river flow and costs. Different weather gives another series of wet and dry years. Each finished run is added to the results table.
Parameters you can change
- Rainfall compared with the long-term average 60–140 %
- Starting population of the southern basin 1–8 million people
- Population growth rate 0–4 %/year
- Irrigated area 0–150 thousand ha
- Income level of the region Low, Middle, High
- Climate trend Stable, Drying (rainfall −0.7% a year)
- Build a dam and reservoir
- Transfer water from the northern basin
- Seawater desalination plant
- Drill more boreholes for groundwater
- Water saving (drip irrigation, leak repair, meters)
Questions to explore
- Why is the southern basin short of water even though the whole region has more water than it needs?
- Drilling more boreholes solves the shortage fastest; what happens to the water table and shallow wells after 30 years?
- With a low income and 140% rainfall, what type of water scarcity does the region have, and which solution fits it?
