HYDROLOGIC PROCESSES, SCALE, CLIMATE VARIABILITY, AND WATER RESOURCES FOR SEMIARID WATERSHED MANAGEMENT
Location: Southwest Watershed Research
Title: Spatial patterns in thunderstorm rainfall events and their coupling with watershed hydrological response 1907
| Morin, E. - HEBREW UNIV. JERUSALEM |
| Maddox, R. - UNIVERSITY OF ARIZONA |
| Gao, X. - UNIV. CALIFORNIA IRVINE |
| Gupta, H. - UNIVERSITY OF ARIZONA |
| Sorooshian, S. - UNIV. CALIFORNIA IRVINE |
Submitted to: Advances in Water Resources
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 15, 2005
Publication Date: February 10, 2006
Citation: Morin, E., Goodrich, D.C., Maddox, R.A., Gao, X., Gupta, H.V., Sorooshian, S. 2006. Spatial patterns in thunderstorm rainfall events and their coupling with watershed hydrological response. Advances in Water Resources. 29:843-860.
Interpretive Summary: Arid and semi-arid regions account for approximately one-third of the land mass of earth. These regions are experiencing continued pressure from population growth in many parts of the world. Water is a critical resource in these regions and is often in short supply. Detailed study of water resources and the hydrology of semi-arid regions is important if we are to continue to populate and use these regions. Rainfall estimates from National Weather Service radar shown daily on popular news forecasts are being used for water resource decisions and models. However, the methods to estimate rainfall from radar are not well tested for semi-arid regions. Rainfall observations from the Walnut Gulch Experimental Watershed, operated by the U.S. Dept. of Agriculture, Agricultural Research Service were used in conjunction with radar data to develop conceptual models of the rainfall spatial patterns. The modeled rainfall provides a simplified representation of the rainfall patterns yet retains the essential information to predict runoff and to more clearly understand what features of a rainstorm are important in generating runoff.
Weather radar systems provide detailed information on spatial rainfall patterns known to play a significant role in runoff generation processes. In the current study, we present an innovative approach to exploit spatial rainfall information of air mass thunderstorms and link it with a watershed hydrological model. Observed radar data are decomposed into sets of rain cells conceptualized as circular Gaussian elements and the associated rain cell parameters, namely, location, maximal intensity and decay factor, are input into a hydrological model. Rain cells were retrieved from radar data for several thunderstorms over southern Arizona. Spatial characteristics of the resulting rain fields were evaluated using data from a dense rain gauge network. For an extreme case study in a semi-arid watershed, rain cells were derived and fed as input into a hydrological model to compute runoff response. A major factor in this event was found to be a single intense rain cell (out of the five cells decomposed from the storm). The path of this cell near watershed tributaries and toward the outlet enhanced generation of high flow. Furthermore, sensitivity analysis to cell characteristics indicated that peak discharge could be a factor of two higher if the cell was initiated just a few kilometers aside.