Menu
:
:



Trends in evaporation and Bowen Ratio on urbanizing watersheds in eastern United States

350 210 Stroud Water Research Center

Dow, C.L., and D.R. DeWalle. 2000. Water Resources Research 36(7):1835–1843.

doi: 10.1029/2000WR900062

Abstract

Long-term trends in annual evaporation and watershed Bowen ratio were studied on 51 eastern United States watersheds which had experienced an estimated 0–58% urban/residential development between 1920 and 1990. Annual watershed evaporation was estimated as the difference between annual streamflow and average watershed precipitation, corrected for watershed elevation effects and gage catch error. Annual watershed Bowen ratios were estimated using spatially and temporally averaged net radiation values and annual evaporation. Significant (α = 0.1) positive trends in annual watershed Bowen ratio and negative trends in evaporation were found for 12 and 10 watersheds, respectively, of 28 watersheds with >2% urban/residential development and only 2 and 3 watersheds, respectively, of 23 watersheds with <2% development. Trend results lead to estimates of the overall change in water and energy balances which were separately related to the percentage change in urban/residential area for all 51 watersheds. These regional relationships, linking watershed hydrology, energy exchange, and land use changes, showed significant decreases in watershed evaporation and significant increases in sensible heating of the atmosphere with increased urban/residential development on watersheds in the eastern United States. At 100% urbanization the regional relationships predicted a decrease in annual evaporation of 22 cm and an increase in the sensible heating of the atmosphere of 13 W/m2.

Give the Gift of Fresh Water

As you give thanks for the gifts in your life, we invite you to give the gift of water. Clean drinking water, good health, happy trout, productive soil, clean air, the simple joys of swimming, boating, fishing — our healthy freshwater ecosystems make these and so many other things possible.

Your donation today will help preserve and protect
the future of fresh water.