Animals & nature · 2021
How could heavy rain after a long drought affect sediment and nutrients entering a drinking-water source?
It could wash accumulated sediment and nutrients into surface water, potentially threatening drinking-water supplies. A computer modeling study of land draining into the Miyun Reservoir found this risk under the RCP 8.5 climate scenario, but the effects varied greatly with rainfall patterns and depended on how wet the soil was before the rain.
Details
Researchers used outputs from five climate models to simulate water flow and water quality in an upstream area that drains into the Miyun Reservoir. Under RCP 8.5, the model projected increases in temperature, rainfall intensity, the frequency of heavy rain and rainstorms, and drought duration, along with greater amounts of sediment and nutrients carried into water.
The central finding was that prolonged drought and subsequent intense rain can interact: rain can mobilize material that has accumulated during the dry period. The outcome depended on the soil's initial moisture, the length of the preceding drought, and the amount and intensity of rain. Effects differed greatly across rainfall patterns, so the study does not imply that every storm after a drought produces the same pollution response. These are conditional model projections, not observations of contamination in drinking water; the abstract gives neither numerical effect sizes nor a clearly specified comparison baseline.
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