Infiltration of water into two soils measured at radial distances from the stems of paloverde (Cercidium microphyllum) and creosote bush (Larrea tndentata) were found to average nearly three times greater under plants than in the openings. Bulk density was lower and organic matter content was higher in topsoil under plants than in the openings.

A conceptual and digital model of the aquifer, with estimates of the aquifer's capability to provide water for rice irrigation through the year 2000Open-File Report Prepared in cooperation with the ARKANSAS GEOLOGICAL COMMISSION Little Rock, Arkansas

Two sets of hydrologic indices were developed to characterize the water-budget components of nontidal wetlands. The first set consisted of six water-budget indices for input and output variables, and the second set consisted of two hydrologic interaction indices derived from the water-budget indices. The indices then were applied to 19 wetlands with previously published water-budget data. Two trilinear diagrams for each wetland were constructed, one for the three input indices and another for the three output indices. These two trilinear diagrams then were combined with a central quadrangle to form a Piper-type diagram, with data points from the tfilinear diagrams projected onto the quadrangle. The quadrangle then was divided into nine fields that summarized the wate~budget information. Two quantitative "interaction indices" were calculated from two of the six water-budget indices (precipitation and evapotranspiration). They also were obtained graphically from the water-budget indices, which were first projected to the central quadrangle of a Piper-type diagram from the flanking trilinear plots. The first interaction index (I) defines the strength of interaction between a wetland and the surrounding ground-and surface-water system. The second interaction index (S) defines the nature of the interaction between the wetland and the surrounding ground-and surfacewater system (source versus sink). Evaluation of these indices using published wetland water-budget data illustrates the usefulness of the technique.

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:°F =(1.8×°C)+32 Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:°C =(°F-32)/1.8 Vertical coordinate information is referenced to the North American Vertical Datum of 1929 (NGVD 29). Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83). Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times aquifer thickness in feet [(ft 3 /d)/ft 2 ]ft. In this report, the mathematically reduced form, foot squared per day (ft 2 /d), is used for convenience. ACCL Acceleration variable for SIP solver in MODFLOW GIS Geographic information system GSB Great Sandy Bottom LMG Algebraic multigrid solver in the Link-AMG (LMG) Package of MODFLOW

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