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Last modified
7/28/2009 2:28:59 PM
Creation date
1/15/2007 1:23:35 PM
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Weather Modification
Project Name
Journal of Weather Modification Abstract
Title
Simulations of Snowpack Augmentation in the Colorado Rocky Mountains
Prepared For
Weather Modification Association
Prepared By
William Cotton, Colorado State University
Date
5/1/2006
State
CO
Weather Modification - Doc Type
Scientific Study
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<br />66 <br /> <br />JOURNAL OF WEATHER MODIFICATION <br /> <br />Volume 38 <br /> <br />APPLICATION OF A HYDROLOGIC MODEL TO ASSESS THE EFFECTS OF CLOUD SEEDING <br />IN THE WALKER RIVER BASIN OF NEVADA <br /> <br />Douglas P. Boyle, Gregg W. Lamorey, and Arlen W. Huggins <br />Desert Research Institute <br />Reno, Nevada <br /> <br />Abstract. The focus of this study is to use a physically-based, distributed hydrologic model to estimate the <br />impacts of cloud seeding efforts on the streamflow generated within the areas of the Walker River Basin <br />targeted by the Nevada seeding program. The hydrologic model is calibrated using GIS information, model <br />default values, and manual calibration to fit observed streamflow at a USGS surface water station within the <br />Walker River Basin. The calibrated model is then used in two case studies that are designed to simulate a non- <br />seeded condition and a seeded condition with a 10% increase in precipitation on the five target areas. The <br />results from the two modeling case studies indicate that the additional precipitation applied in the seeded case <br />results in increases in evaporation and runoff from the target areas but does not significantly impact the storages <br />of moisture in the groundwater and soil zone for all of the five target areas. The fraction of seeding-increased <br />precipitation that resulted in streamflow varied from 49% to 89% among the different target areas. The <br />remainder of the additional precipitation resulted in evapotranspiration from the target areas. <br /> <br />1. INTRODUCTION AND SCOPE <br /> <br />There are more than a dozen wintertime cloud <br />seeding programs in the western U.S. whose <br />primary goal is to increase snowfall over specific <br />drainage basins in order to subsequently increase <br />stream runoff in the spring and summer months. <br />An accurate assessment of the impacts of any cloud <br />seeding operation on streamflow runoff requires <br />detailed knowledge of the spatial and temporal <br />increases in precipitation due to the cloud seeding <br />activities and the watershed response to the <br />additional precipitation. Obtaining this knowledge <br />is often difficult or impossible due to the budget <br />and time constraints associated with the field effort <br />required to collect the necessary data. For projects <br />in the western U.S. the documentation of seeding <br />effects has been accomplished by assessments of <br />randomized experiments such as in Mooney and <br />Lund (1969), and by highly focused <br />nonrandomized experiments. Latter experiments <br />studied in-cloud microphysical changes, snowfall <br />characteristics and precipitation rate changes at the <br />surface, and evidence of the seeding material in <br />snow layers in seeding target areas (e.g., Super, <br />1999, Deshler et al., 1990 and Warburton et aI., <br />1996). Some operational projects have compared <br />stream runoff from seeded and unseeded basins as <br />part of their evaluation (Henderson, 1966). Also, <br />McGurty (1999) used snow chemistry and a <br />relationship between snow density and silver <br />concentration to estimate increases in snowfall and <br />runoff in a Sierra Nevada target area. While the <br />prediction of additional runoff due to seeding <br />efforts has not been routinely attempted, there have <br />been preliminary studies conducted in the Upper <br />Colorado River Basin (Super and McPartland, <br />1993 ). <br /> <br />- Reviewed - <br /> <br />Within Nevada's Weather Damage Modification <br />Program (WDMP), a cooperative research effort <br />with the U.S. Bureau of Reclamation (Hunter et al., <br />2005), hydrologic modeling has been incorporated <br />into the research to predict how changes in the <br />snowpack from cloud seeding will alter runoff in <br />the affected streams of targeted basins. This <br />research involves the application of a hydrologic <br />model to simulate watershed response to additional <br />precipitation from cloud seeding activities through <br />the different hydrologic processes (snowpack <br />evolution, evaporation and transpiration, <br />infiltration, soil moisture movement, runoff, and <br />streamflow). This research component was "piggy- <br />backed" onto cloud seeding operations that are <br />routinely conducted in the Walker Basin by the <br />State of Nevada. <br /> <br />This paper presents results from the hydrologic <br />modeling of the Walker River Basin whose <br />headwater region is on the eastern (mainly <br />downwind) side of the Sierra Nevada just north of <br />Yosemite National Park. During the winter of <br />2003-04 this headwater region was targeted by <br />several ground seeding generators and occasionally <br />by aircraft seeding. The hydrologic model is <br />initially calibrated during a period when there were <br />no known cloud seeding operations. Next, the <br />hydrologic model is used to investigate the impacts <br />of cloud seeding in the Walker River Basin through <br />two case studies. In the first case study. the model <br />is run forward in time through the 2003-04 winter, <br />assuming the target areas are not impacted by <br />ground or aircraft cloud seeding activities. In the <br />second case, cloud seeding activities are assumed <br />to increase the total precipitation on the target areas <br />during the 2003-04 winter by 10%. Although <br />storms over the Walker Basin were routinely <br />seeded in 2003-04 and snow profiles verified the <br />
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