In many places huge dams retain river water and rainwater ​ — a measure that has proved somewhat effective, even though reservoirs in arid areas may lose about 10 percent of their water through evaporation.
Di banyak tempat, bendungan - bendungan raksasa menampung air sungai dan air hujan ​ — metode yang sedikit banyak terbukti efektif, meskipun reservoir di daerah gersang bisa menyusut sekitar 10 persen karena penguapan.