Because of growing interest in the role of lakes and wetlands in the hydrology of the prairie environment, a group of wetlands in the Cottonwood Lake area, Stutsman County, N. Dak., are being instrumented for long-term hydrologic studies. The study site is on a regional topographic high near the eastern edge of the Missouri Coteau and is underlain by more than 400 feet of glacial drift, largely silty, clayey till. Long-term climatic data indicate the study area is in a water deficient area--mean annual evaporation exceeds mean annual precipitation by about 18 inches. Different methodologies are being used to compare measurements and estimates of each hydrologic component interacting with the lakes and wetlands. For example, for a 3-month period in 1979, estimates of precipitation for the study site using data collected at National Weather Service stations differed from that measured by a recording gage at the study site by several tenths of an inch for 14-day totals and differed by more than half an inch for individual storms. Numerical simulation analysis of regional groundwater flow systems shows the study site is situated in a regional recharge area, but local groundwater flow systems can discharge to lakes and wetlands within the recharge area. Instrumentation at the study site shows a complex interrelation of wetlands and groundwater. Based on data for 1979 only, some wetlands appear to recharge groundwater, some wetlands are flow-through types where groundwater enters one side and surface water seeps to groundwater on the other side, and some wetlands are discharge points for groundwater. Further, these interrelations vary throughout the year.

Numerical simulation models have become indispensable in hydro- and environmental sciences and engineering. This monograph presents a general introduction to numerical simulation in environment water, based on the solution of the equations for groundwater flow and transport processes, for multiphase and multicomponent flow and transport processes in the subsurface as well as for flow and transport processes in surface waters. It displays in detail the state of the art of discretization and stabilization methods (e.g. finite-difference, finite-element, and finite-volume methods), parallel methods, and adaptive methods as well as fast solvers, with particular focus on explaining the interactions of the different methods. The book gives a brief overview of various information-processing techniques and demonstrates the interactions of the numerical methods with the information-processing techniques, in order to achieve efficient numerical simulations for a wide range of applications in environment water.