RESPONSE FUNCTIONS OF CROPS YIELD TO SOIL MOISTURE STRESS1

: A methodology for determining an optimal irrigation policy to obtain maximum economic yield of crops is presented. The method is based on an empirical response function, relating crop yield to soil moisture stress in different stages of plant growth. The function was developed from data obtained in field experiments on several crops and may be useful in determining when and how much to irrigate. Additionally, a mathematical expression is derived from that function which estimates the economic loss if irrigation is not applied in the opportune moment.     

PREPLANTING SOIL MOISTURE USING PASSIVE MICROWAVE SENSORS1

ABSTRACT: Accurate assessment of preplanting soil moisture conditions is necessary for good agricultural management, and can have a significant influence on crop yield in the Texas Panhandle region. The Texas High Plains Underground Water Conservation District invests considerable time and money in developing a soil moisture deficit map each year in the hopes of achieving optimal use of irrigation water. Microwave sensors are responsive to surface soil moisture and, if used in this application, can provide timely and detailed information on root zone soil moisture. For this reason, an experiment was conducted in 1984 to evaluate the potential of aircraft-mounted passive microwave sensors. Microwave radiometer data were collected over a 2700 km² area near Lubbock, Texas, with a processed resolution of 0.32 km². These data were ground registered and converted to estimates of soil moisture using an appropriate model and land cover and soil texture information. Analyses indicate that the system provides an efficient means for mapping variations in soil moisture over large areas.     

ESTIMATION OF SOIL MOISTURE WITH API ALGORITHMS AND MICROWAVE EMISSION1

Large area soil moisture estimations are required to describe input to cloud prediction models, rainfall distribution models, and global crop yield models. Satellite mounted microwave sensor systems that as yet can only detect moisture at the surface have been suggested as a means of acquiring large area estimates. Relations previously discovered between microwave emission at the 1.55 cm wavelength and surface moisture as represented by an antecedent precipitation index were used to provide a pseudo infiltration estimation. Infiltration estimates based on surface wetness on a daily basis were then used to calculate the soil moisture in the surface 0–23 cm of the soil by use of a modified antecedent precipitation index. Reasonably good results were obtained (R²= 0.7162) when predicted soil moisture for the surface 23 cm was compared to measured moisture. Where the technique was modified to use only an estimate of surface moisture each three days an R² value of 0.7116 resulted for the same data set. Correlations between predicted and actual soil moisture fall off rapidly for repeat observations more than three days apart. The algorithms developed in this study may be used over relatively flat agricultural lands to provide improved estimates of soil moisture to a depth greater than the depth of penetration for the sensor.     

SOIL MOISTURE SENSING WITH AIRCRAFT OBSERVATIONS OF THE DIURNAL RANGE OF SURFACE TEMPERATURE1

ABSTRACT: Aircraft Observations of the surface temperature were made by measurements of the thermal emission in the 8-14 μm band over agricultural fields around Phoenix, Arizona. The diuranal range of these surface temperature measurnments were well correlated with the ground measurment of soil moisture in the 0-2 cm layer. The surface temperature indicating no moisture stress. These results indicate that for clear atmospheric conditions remoteley sensed sufrace temperatures can be a reliable indicator of soil moisture conditions and crop status.     

SOIL WATER CHARACTERISTICS OF TWO SOIL CATENAS IN ILLINOIS: IMPLICATIONS FOR IRRIGATION1

ABSTRACT: Soil water was monitored by neutron scattering in six soils, three each within two drainage catenas in east-central Illinois, over a 15-month time span. The prairie soils have formed in: (1) 76–152 cm of silt loam, eolian sediments (bess) over glacial till (Catlin-Flanagan-Drummer catena), and (2) bess greater than 152 cm in thickness (Tama-Ipava-Sable catena). We characterized the water content of these soils over the total time span and for wet and dry climatic subsets, as an aid to potential irrigation decisions. Soils of the thin bess, C-F-D catena dried out to lower water contents and had greater soil water variability than did the thick bess soils. Under wet conditions, soil water contents in the two catenas were quite similar. Alleviation of surface and subsurface drying via irrigation would thus be more advantageous to yields on the C-F-D soils than on the T-I-S soils.     

ESTIMATES OF THE ECONOMIC VALUE PRODUCTIVITY OF IRRIGATION WATER IN PAKISTAN FROM FARM SURVEYS1

Data from two cross-sectional surveys totaling over 2000 farmers in Pakistan are analyzed with regression techniques to estimate the value productivity of irrigation water and related resources. Returns to irrigation water vary by province, but in general are found to be high relative to estimated costs of obtaining water. Salinity of water supplies is an important productivity depressant. The results will be useful in determining the economic feasibility of various means for augmenting supplies and for improving delivery and application efficiencies.     

ALLOCATION PROCEDURE OF WATER AND LAND RESOURCES IN RELATION TO SOME IRRIGATION QUALITY PARAMETERS1

ABSTRACT: Land, water, labor, and capital are optimally allocated to crops on a farm, using a procedure that also relates to irrigation frequency and level of improvement in the irrigation system. The procedure is based on formulating outputs and expenditures as well as the functions of irrigation frequency-water and yield. The Generalized Geometric Programming is used to solve the objective function as nonlinear equations are involved.     

SUPPLEMENTAL IRRIGATION OF HORTICULTURAL CROPS IN THE HUMID REGION1

ABSTRACT: A computer model was developed in order to establish a yield predictive relationship and to estimate the water requirements for supplemental irrigation of horticultural crops in the humid region. Alternative distribution systems were developed and designed using the results from the computer model and Wood's (1980) pipe network algorithm. The capital, operational, and maintenance costs of the distribution and recommended on-farm irrigation systems were determined and used to evaluate the economic feasibility of the alternative designs. Results show that the concentration of irrigated area along the distribution system, the length of the distribution system, and cropping system all have an important effect on the economic feasibility of supplemental irrigation in Wayne County, Kentucky.     

THE IMPORTANCE OF SOIL IN EVALUATING POTENTIAL WASTE WATER DISPOSAL SITES IN THE MISSOURI OZARKS1

ABSTRACT: A number of criteria can be used in the selection of an area for the irrigation disposal of secondary treated waste water. The inherent capacity of the surface soil to retain, or at least detain, the various nutrient ions passing through the profile in the percolating waters becomes the prime consideration in regions with shallow water tables or in Karst areas such as the Missouri Ozarks where the risk of ground water supply contamination is high. A comprehensive study of the nutrient renovation potential of several soils was undertaken at a proposed effluent irrigation site along the Ozark National Scenic Riverways in south central Missouri. The surface soil hydrology was evaluated employing selected soil water parameters. Exchange equilibria studies determined the retention capacity for Ca and Mg while the concentrations of other selected ions were analyzed in the soil water to measure their retention time and net removal. The movement of a bromine tracer was monitored as an index of the renovation capacity of these soils for the more mobile anions such as nitrate. Neutron activation analysis proved to be a useful tool in the water quality analyses. All surface soil profiles demonstrated some degree of nutrient renovation for the various nutrients studied.     

CENTER PIVOT IRRIGATION IN THE COLUMBIA BASIN OF WASHINGTON AND OREGON: DYNAMICS AND IMPLICATIONS1

ABSTRACT: As of 1976 over 225,000 acres were being irrigated by center pivot units in a five-county area of the Columbia Basin in Oregon and Washington. Most of the development took place since 1970. Dynamic application of center pivot technology altered the concept of irrigability in the study area, converting lands that were often rolling, sandy, and plagued by wind erosion from low grade grazing to productive irrigated units. This development was entirely by private enterprise, with large corporate farms accounting for much of the effort. Little prior comprehensive planning or coordination took place. When the circulation of water is altered on such a massive scale, however, unplanned impacts may be far reaching. In this case they include:1) acceleration of the shift to high cost thermoelectric generation, 2) alteration of state institutions designed to allocate water, and 3) possible significant alterations of the socioeconomic fabric of small rural service centers.     

USING INFILTRATION ENHANCEMENT AND SOIL WATER MANAGEMENT TO REDUCE DIAZINON IN RUNOFF1

ABSTRACT: Pesticide runoff from dormant sprayed orchards is a major water quality problem in California's Central Valley. During the past several years, diazinon levels in the Sacramento and San Joaquin Rivers have exceeded water quality criteria for aquatic organisms. Orchard water management, via post‐application irrigation, and infiltration enhancement, through the use of a vegetative ground cover, are management practices that are believed to reduce pesticide loading to surface waters. Field experiments were conducted in Davis, California, to measure the effectiveness of these management practices in reducing the toxicity of storm water runoff. Treatments using a vegetative ground cover significantly reduced peak concentrations and cumulative pesticide mass in runoff for first flush experiments compared with bare soil treatments. Post‐application irrigation was found to be an effective means of reducing peak concentrations and cumulative mass in runoff from bare soil treatments, but showed no significant effect on vegetated treatments.     

USE OF DELPHI METHODOLOGY TO ASSESS GOALS AND SOCIAL IMPACTS OF A WATERSHED PROJECT1

ABSTRACT: The major objective is to report the way the Delphi methodology was employed in an environmental study aimed at identifying and ranking goals and social impacts of Cooper Dam and Reservoir Project located in the East Texas area. The Delphi procedures were modified to accommodate the nature of social field under study. Data were collected through personal interviews from twenty-seven respondents representing the government agency responsible for planning the Project and three communities geographically contiguous to the project. The respondents were provided an initial list of the Project's goals and social impacts and were asked to rank them in terms of degree of importance and to add to the list other goals and impacts that they would consider necessary. Respondents were interviewed in two successive rounds. Data show that on the whole the Delphi procedures were helpful in action analysis of the Project by identifying and ranking its goals and social impacts in terms of selected criteria.     

VERIFICATION AND APPLICATION OF REGIONAL EQUATIONS FOR THE STORAGE FUNCTION RUNOFF MODEL1

The storage function model is a nonlinear rainfall-runoff model that has been developed for and applied to flood runoff analysis in Japan. This paper extends the model applicability by developing practical equations for estimating model parameters which are appropriate on a regional basis, i.e., so-called regional equations. Previously, the parameters were computed from historical data for a specific basin or from relationships that do not account for land use and topography. To develop the regionalized equations, model parameters were identified for 91 flood events from 22 watersheds in Japan by applying a mathematical optimization technique. Results from 39 of these events were statistically compared and regional relationships were determined as a function of land use, basin area and rainfall intensity. The utility of the estimated equations were tested by computing runoff hydrographs for lumped basins. The estimated parameters were also applied in a distributed watershed model formulation. Both applications showed acceptable results that validate the use of the regionalized relationships.     

USING SOIL TEXTURE TO ESTIMATE SATURATED HYDRAULIC CONDUCTIVITY AND THE IMPACT ON RAINFALL-RUNOFF SIMULATIONS1

ABSTRACT: In this paper a new set of soil texture data is used to estimate the spatial distribution of saturated hydraulic conductivity values for a small rangeland catchment. The estimates of conductivity are used to re-excite and re-evaluate a quasi-physically based rainfall-runoff model. The performance of the model is significantly reduced with conductivity estimates gleaned from soil texture data rather than the infiltration data used in our previous efforts.     

HYDROLOGIC LANDSCAPES ON THE DELMARVA PENINSULA PART 2: ESTIMATES OF BASE-FLOW NITROGEN LOAD TO CHESAPEAKE BAY1

ABSTRACT: Base-flow samples were collected from 47 sampling sites for four seasons from 1990–91 on the Delmarva Peninsula in Delaware and Maryland to relate stream chemistry to a “hydrologic landscape” and season. Two hydrologic landscapes were determined: (1) a well-drained landscape, characterized by a combination of a low percentage of forest cover, a low percentage of poorly drained soil, and elevated channel slope; and (2) poorly drained landscape, characterized by a combination of an elevated percentage of forest cover, an elevated percentage of poorly drained soil, and low channel slope. Concentrations of nitrogen were significantly related to the hydrologic landscape. Nitrogen concentrations tended to be higher in well-drained landscapes than in poorly drained ones. The highest instantaneous nitrogen yields occurred in well-drained landscapes during the winter. These yields were extrapolated over the part of the study area draining to Chesapeake Bay in order to provide a rough estimate of nitrogen load from base flow to the Bay and its estuarine tributaries. This estimate was compared to an estimate made by extrapolating from an existing long-term monitoring station. The load estimate from the stream survey data was 5 ± 10⁶ kg of N per year, which was about four times the estimate, made from the existing long-term monitoring station. The stream-survey estimate of base flow represents about 40 percent of the total nitrogen load that enters the Bay and estuarine tributaries from all sources in the study area.     

APPLICABILITY OF THE GREEN AND AMPT INFILTRATION EQUATION TO RANGELANDS1

ABSTRACT: The objective of this study was to investigate the use of Green and Ampt infiltration equation parameters (determined by least squares fitting of field infiltration data or predicted from soil texture properties) to characterize infiltration on spatially varying rangeland sites. It was found that a least squares regression approach reduces the physically based parameters in the Green and Ampt to empirical coefficients since negative coefficients are obtained, particularly on plots with low infiltration rates. Green and Ampt parameters predicted from soil texture data describe infiltration rates less than 3 cm/hr. The applicability of these Green and Ampt parameters appears limited to sites with lower infiltration rates. Results indicate that soil texture predictive triangles, developed to describe infiltration on agricultural soils, need revision to adequately describe infiltration patterns on rangelands.     

PLANNING LEVEL ESTIMATES OF THE VALUE OF RESERVOIRS FOR WATER SUPPLY AND FLOW AUGMENTATION IN NEW HAMPSHIRE1

: In general, the choice among reservoirs for water supply or flow augmentation is a multiobjective problem. Choices are based in part on the yield available from water supply reservoirs or, in the case of flow augmentation reservoirs, on the increase in low flows at downstream locations. Detailed estimates of these effects may be too costly for basin planning purposes. Thus this paper presents methods for rapid estimation of those quantities for New Hampshire. For water supply reservoirs, a composite empirical relation between Y95 (the draft available 95 percent of the time) and storage ratio, S*, is developed from previous studies in the region. For flow augmentation reservoirs, empirical relations between S* and degree of regulation, R*, are applied to each upstream regulating reservoir. Values of regulation arc then summed and divided by the mean flow at the downstream reach of interest. This parameter, (ΓR)*, is then related to increase in flow available 95 percent of the time by an empirical relation.     

THE DEVELOPMENT OF A PLAN OF STUDY – AN INTERAGENCY APPROACH TO MULTIOBJECTIVE PLANNING AND EVALUATION OF WATER AND LAND RESOURCE USE1

ABSTRACT The paper presents a systems approach for planning and evaluating alternative plans for resource use incorporating the concepts of multiobjective planning and evaluation (MOPE). The need for multidisciplinary input and strong interagency cooperation in planning for resource use is related to the logical and orderly completion of the planning steps. The paper briefly describes MOPE, emphasizing two important concepts: (1) the relationship of the study problems and objectives to national social objectives, and (2) the display of alternative solutions showing tradeoffs. Several important characteristics of a plan of study which implements MOPE are presented and discussed. A proposed MOPE analytical system is discussed in detail. The MOPE analytical system is divided into eight interdependent subsystems that describe data collection, use, analysis, and results. A linear program (L.P.) model is proposed to analyze the present and future demand relationships for natural resources. The model will also evaluate the interaction of agriculture, forestry, and recreation with the resource base of the basin, considering National Economic Development, Environmental Quality, and Regional Development.     

THE INFLUENCE OF SPRING AND FALL TEMPERATURES ON THE AVOIDANCE RESPONSE OF JUVENILE ATLANTIC MENHADEN,BREVOORTIA TYRANNUS,EXPOSED TO SIMULTANEOUS CHLORINE-δT CONDITIONS1

ABSTRACT: The avoidance response of groups of juvenile Atlantic menhaden, Brevoortia tyrannus, was evaluated by exposing test species to a range of simultaneous total residual chlorine (TRC) (0.00, 0.05, 0.10, and 0.15 mg/L) and elevated temperature (0, 2, 4, and 6°C) conditions simulating power plant discharges. This species was tested at both 15 and 20°C to determine possible effects of acclimation temperature on the avoidance response. These temperatures were selected to represent spring or fall thermal conditions when most East Coast power plant facilities initiate power plant chlorination in the spring or terminate the use of this biocide in the fall. An unbalanced 3-factor factorial design was used to develop response surface avoidance models at 15 and 20°C. The model developed at 15°C showed: (1) an increase in avoidance occurred at all δT conditions as TRC increased from 0.00 to 0.05 mg/L; (2) a greater degree of avoidance occured at TRC concentrations above 0.05 mg/L at all δT conditions; and (3) TRC was the most important term inflencing avoidance. The model for Atlantic menhaden at 20°C showed: 1) avoidance increased with increasing TRC concentration at each δT condition; (2) avoidance did not necessarily increase with increasing δT's at each TRC concentration; (3) greatest avoidance occured at 0°C δT and 0.15 mg/L TRC; and (4) TRC was the most important term influencing avoidance. There was a significant difference (p < 0.00001) between avoidance models at 15 and 20°C. However, when extreme conditions of 0.15 mg/L TRC and 0–6°δT were compared, the degree of avoidance responses (percent time in control area) was similar.     

THEORY,DEVELOPMENT, AND UTILIZATION POTENTIAL OF THE BIOMILIEU CONCEPT1

The paper presents a quantitative engineering approach to analysis of total environment allowing for simultaneous consideration of a theoretically infinite number of quality indicators and physiological requirements. It discusses theory and fundamentals of a two-dimensional space and time function solution concerning a small estuarine-type environment. A three dimensional solution is indicated. Input data may range from reconnaissance-type to the outputs of mathematical transport models. Applications are discussed with respect to environmental quality problems, availability of suitable data, and some areas of research where results could find immediate application.