A sophisticated, user-friendly computer model developed by ARS researchers has helped engineers, scientists, and students worldwide understand how water and chemicals move in soil and groundwater. HYDRUS allows agricultural engineers to design irrigation systems that provide optimal water to crops, while minimizing the transport of fertilizers and pesticides to groundwater. Landfill designers have used the program to ensure their facilities do not release contaminants. Dozens of scientists and students contributed to HYDRUS, which was developed at ARS' George E. Brown, Jr., Salinity Laboratory in Riverside, CA. Thanks to a cooperative research and development agreement with the Colorado School of Mines' International Ground Water Modeling Center (IGWMC) in Golden, the model continues to evolve. IGWMC distributes the model, provides hands-on help to users, runs short courses on the model, and gives feedback to ARS so the researchers can improve HYDRUS. So far, IGWMC has sold more than 500 copies of the model worldwide. HYDRUS is an easy-to-use, Windows-based format. It displays results visually by means of graphs or contour lines, instead of as columns of numbers. Animation can illustrate how a fertilizer or other chemical would move through the soil and possibly into groundwater.

Soil Physics and Pesticide Research Unit, Salinity Laboratory, Riverside, CA
Rien van Genuchten, (909) 369-4847, rvang@ussl.ars.usda.gov

Designing rock chutes has been made easier—with fewer design errors—thanks to a new computer program. Rock chutes are loose rock structures built at water resource construction sites to safely convey water to lower elevations. Natural Resources Conservation Service engineers are using a computerized design procedure developed by ARS researchers. It helps them to more quickly and accurately predict the best design for a given chute size and flow rate. Intended for use with Excel in Microsoft Office 97, the program addresses many additional features needed to design low-cost, environmentally sensitive hydraulic structures. For example, the program can calculate the amount of rock necessary to construct the chute and provide a cost estimate. It should accelerate the application of rock chute technology. A free copy of the program can be downloaded at the web address. Go to http://www.ia.nrcs.usda.gov/design and link to Engineering Programs. It is listed under the name "Rock Chute Design Program." This design tool should be useful to consulting engineers and water resource managers.

Hydraulic Engineering Research Laboratory, Stillwater, OK
Kerry M. Robinson, (405) 624-4135, ext. 225, krobinson@pswcrl.ars.usda.gov