Tham khảo tài liệu 'earth sciences - notable research and discoveries part 8', khoa học tự nhiên, địa lý phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 148 EARTH SCIENCES different types. Hans-Jorg Vogel of the Helmholtz Centre for Environmental Research UFZ in Leipzig Germany and Olaf Ippisch at the University of Stuttgart in Germany recently refined models of these flows. Many of these models are based on a mathematical formula called Richards equation which is limited in how large an area it accurately models. At large scales a large section of ground the model must be broken up into discrete partitions of a certain size otherwise it is inaccurate. Vogel and Ippisch found a way of estimating the size of these partitions so that the models would be correct. The researchers published their findings Estimation of a Critical Spatial Discretization Limit for Solving Richards Equation at Large Scales in a 2008 issue of Vadose Zone Journal. Scientists are also monitoring aquifers to collect even more data. As crucial sources of water for many regions aquifer depletion would have serious consequences. For example the largest aquifer in North America the Ogallala Aquifer lies under parts of eight American states Texas New Mexico Oklahoma Colorado Kansas Nebraska Wyoming and South Dakota . A lot of farms and homes rely on this water. Ogallala s supply is dwindling as estimated by the United States Geological Survey USGS and although it is continually recharged replenishment happens slowly and over a limited area. Dennis Gitz of the Agricultural Research Service and his colleagues at Texas Tech University are monitoring the flow of water through the soil around the aquifer with soil thermometers the presence of water alters the soil s temperature . The researchers are focusing on playa lakes temporary lakes formed when rainwater collects in a cavity to see if water filtering through the soil at these points is contributing much clean water to the aquifer. If so then the playa lake region must be maintained and protected. Gitz and his colleagues have begun the study by installing sensors at 14 playa lakes and are preparing
