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Deciphering the effects of land use on environmental quality requires detailed knowledge of the processes governing soil and landscape genesis. The objective of this study was to describe the landscape evolution and shallow groundwater hydrology of a glaciated landscape in Iowa and to relate the soil color pattern to water table fluctuations. Stratigraphic and geomorphic maps and cross sections were prepared using characterization data from 128 soil cores collected from a 32‐ha site. One transect crossing several hillslopes was instrumented with 47 piezometers to determine groundwater flow direction. Three strata of surficial sediments overlying till were identified. The upper two strata were slope alluvium deposited after 4300 YBP, which limits the age of the soils to the late Holocene or younger. The lower sediment resembled alluvium and may be supraglacial sediment draped on the till and later eroded from adjacent hillslopes. The hydrology was characterized by recharge under topographic highs, lateral groundwater flow on sideslopes and discharge in swales. During dry periods, however, portions of higher swales acted as recharge areas and groundwater flow was directed between swales. Morphologic indicators of wetness are better expressed and shallower in soils at footslope and toeslope positions, but some of these features are relict because of the lowering of the water table by artificial drainage.

A series of three wetlands in a local recharge‐throughflow‐discharge groundwater flow system were investigated to determine factors controlling concentration of gypsum at the wetland edge. The three wetlands differ in pond size, permanence, salinity, and in their relationship to the groundwater hydrology. We believe gypsum accumulation resulted from long term hydrologic, geomorphic, and climatic factors. Wetland salinity appeared to control the distribution and amount of gypsum in soils around individual wetlands and between wetlands. In all wetlands gypsum was concentrated at the edge; presumably as a result of dissolved salt transport to an area of low water potential created by evapotranspiration and freezing (edge effect). The water flow from the edge effect converged on the peninsulas and diverged in the bays. Consequently in less saline wetlands, the bay soils contained minimal amounts of gypsum; peninsula soils were very gypsiferous. Wetlands of high salinity were surrounded by a continuous band of evaporites including gypsum. Within individual wetlands, differences in the degree and number of ponding events and groundwater recharge‐discharge resulted in variations in gypsum distribution across soils of the low prairie, wet meadow, and shallow marsh vegetation zones.

Hillel. D. 1982. [ncrodu~cion co soil physics. Acade• mic Press. :-:ew York. Jury. W.A .. and E.E. ,\tiller. 1974 , 'vfeasuremenc of che cransporc coefficients for coupled How of h"c •nd moisture 1n a rr:edium soil. Soil Sci• ence Sociery of Amer~ca Proceedings 38:55l-55i.

Abstract. Accurate information on the distribution of the surface energy balance components in arid riparian areas is needed for sustainable management of water resources as well as for a better understanding of water and heat exchange processes between the land surface and the atmosphere. Since the spatial and temporal distributions of these fluxes over large areas are difficult to determine from ground measurements alone, their prediction from remote sensing data is very attractive as it enables large area coverage and a high repetition rate. In this study the Surface Energy Balance Algorithm for Land (SEBAL) was used to estimate all the energy balance components in the arid riparian areas of the Middle Rio Grande Basin (New Mexico), San Pedro Basin (Arizona), and Owens Valley (California). We compare instantaneous and daily SEBAL fluxes derived from Landsat TM images to surface-based measurements with eddy covariance flux towers. This study presents evidence that SEBAL yields reliable estimates for actual evapotranspiration rates in riparian areas of the southwestern United States. The great strength of the SEBAL method is its internal calibration procedure that eliminates most of the bias in latent heat flux at the expense of increased bias in sensible heat flux.

Hillel. D. 1982. [ncrodu~cion co soil physics. Acade• mic Press. :-:ew York. Jury. W.A .. and E.E. ,\tiller. 1974 , 'vfeasuremenc of che cransporc coefficients for coupled How of h"c •nd moisture 1n a rr:edium soil. Soil Sci• ence Sociery of Amer~ca Proceedings 38:55l-55i.

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