HR: 1330h
AN: H32C-0588    [PDF]
TI: Irrigation Induced Changes in Areal Evapotranspiration in Southeastern Turkey: Test and Application of Bouchet's Complementary Relationship
AU: * Ozdogan, M
EM: ozdogan@bu.edu
AF: Boston University Department of Geography, 675 Commonwealth Avenue, Boston, MA 02215 United States
AU: Salvucci, G D
EM: gdsalvuc@bu.edu
AF: Boston University Department of Geography, 675 Commonwealth Avenue, Boston, MA 02215 United States
AB: Recent study using satellite data in Southeastern Turkey reveals that irrigated lands have expanded up to 300 percent over the course of ten years. Such large-scale expansion of irrigation is expected to have had a large influence on the regional hydrologic cycle by significantly altering evaporating conditions. However, to date, the existence and the magnitude of such modifications largely remain unknown. To quantify such impacts, we used statistical analysis of long-term meteorological observations as well as models of evaporation specifically suited to changing soil moisture supply, all within the context of Bouchet's complementary relationship. The hypothesis of complementary relationship states that over a large homogeneous surface is negligible, the actual areal evaporation and the potential evaporation are in a complementary relationship, provided the energy balance of the surface remains constant. This hypothesis could provide the tools to quantify irrigation induced changes in partitioning of water between the land surface and the atmosphere. As well, it provides the appropriate tools to calculate actual evaporation based on routine meteorological observations. To determine whether pronounced changes in evaporating conditions due to large-scale irrigation exist within a large agricultural plain in semi-arid Southeastern Turkey, we used 27-year seasonal meteorological observations of temperature, humidity, wind speed, and radiation within the framework of complementary theory. Results indicate that the potential evaporation has decreased from about 10 mm/day to about 5 mm/day, closely following the increase in irrigation over the same period. This decline in potential evaporation is a result of a decrease in wind speed and increase in humidity. These results indicate that the rapid expansion of irrigation in Southeastern Turkey has strongly modified the lower atmosphere in a way that appears consistent with Bouchet's complementary theory. Future work will include quantification of actual evaporation as a function of irrigated land area using both observational data and results from simulation analyses with a meso-scale climate model.
DE: 0315 Biosphere/atmosphere interactions
DE: 1803 Anthropogenic effects
DE: 1833 Hydroclimatology
DE: 1836 Hydrologic budget (1655)
DE: 1878 Water/energy interactions
SC: Hydrology [H]
MN: 2003 Fall Meeting