ROLE OF IRRIGATION WATER IN AGRICULTURAL PRODUCTION: SOME RESOURCE USE ISSUES1

ABSTRACT: A partial production function for corn that considers the time and amount of water applications is determined. Examples are worked out by using data on site specific parameters for nine soil sites in the Great Plains Region repesenting various combinations of water holding capacity, pan evaporation, and average rainfall. It is found that soils with a low water holding capacity are more water and energy intensive in crop production and thus more vulnerable to fluctuations in net returns due to declining water tables or energy shortages. Despite this, farmers of low water holding capacity soils are likely to opt for irrigation. This points to the existence of a necessary, but sufficient, condition for socially inefficient use of ground water resources. This calls to question the property right concept in water created through the appropriation doctrine and the “law of capture.” This paper indicates the type of analysis that must be undertaken in order to make appropriate changes in laws governing water use.     

石油烃在水面上蒸发过程的研究

原油溢流到水体后对水体造成污染。研究油污的转化规律对于污染事故评价、污染治理方面有着非常重要的意义。通过对三种不同性质的原油进行的风化和蒸发实验 ,证明三种原油低组分具有很快的蒸发速度 ,4天时间就可蒸发掉90 %以上的原油 ,同时得出了不同原油的蒸发规律。     

水资源研究中几个问题的探讨

本文讨论了区域水资源的评价问题.无论是地表水、地下水,还是土壤水都是来源于大气降水,降水资源才是区域总水资源;同时讨论了区域水资源的平衡原理.降水资源转化了截留水、地表水、土壤水和地下水4项水资源.该文对这2种不同的水体进行了深入讨论,着重论述了土壤水资源的概念及其特征.并对潜水蒸发和水资源的价值问题提出了看法.     

Using nighttime light data to estimate water evaporation inside buildings in China's urban areas

Urbanization has a great impact on urban evapotranspiration. Water evaporation inside buildings is an important part of urban water vapor resources and a crucial core of urban hydrological processes. The systematic studies on building water evaporation (BWE) are mostly the method of experimental monitoring. This study proposed a new method to simulate and estimate water evaporation flux inside buildings in urban areas. Based on the nighttime light data and urban per capita gross domestic product (GDP), a new modeling system was built to simulate the total BWE. Building area was calculated using the nighttime light data. And the BWE coefficient D_f was estimated according to the important indicator of economic development per capita GDP value. Then the water evaporation inside urban buildings and the spatial distribution of water evaporation inside buildings in typical cities could be obtained. The results showed that the total amount of water evaporation inside buildings in China's urban areas was 24.5 billion m³. Among the 31 provincial capitals in China, Shanghai had the largest BWE of 1.08 billion m³. The minimum water evaporation of buildings in Lhasa was 20.0 million m³. Studies of BWE can assess urban water budgets, support on-demand allocation of water resources, and provide a fundamental understanding of the relationship between water resources and energy heat island effects in urban areas.     

The future of water in Australia: The potential effects of climate change and ozone depletion on Australian water quality,quantity and treatability

Water is a resource that is essential for all life on Earth. An exponentially growing human population, in addition to unprecedented industrial and technological development, threaten the availability and quality of this resource. Climate change and ozone depletion are two major environmental problems facing mankind today. These problems have the potential to further strain currently available freshwater resources. Recent research has shown that climate change and ozone depletion are linked phenomena and their interaction exacerbates their impact. Changes in precipitation, surface runoff, solar UV radiation, temperatures, and evaporation are some of the predicted outcomes of climate change and ozone depletion. They influence the biogeochemical cycles and aquatic ecosystems in lakes and rivers, and alter the character of natural organic matter (NOM) and, consequently, they have the potential to affect the quality, quantity and treatability of our water resources. Given these uncertainties, and the need to mitigate the consequences of climate change and ozone depletion, the issues of changing water quality, quantity and treatability cannot be ignored by Australian governments and water utilities.     

ACCOUNTING FOR DISCREPANCIES IN PAN EVAPORATION CALCULATIONS1

ABSTRACT: Four experiments were made to document and account for differences in evaporation data that were calculated using pans equipped with float-activated recorders and pans with hook gauge/rain gauge instrumentation. Paired in-pan comparisons indicated that evaporation differences were not due to the technique of measuring water level within the pan. Also, the recorder float-lag did not account for the differences. By sampling rainfall events, it was found that evaporation pans and standard (8 in. orifice) rain gauges record significantly different amounts of rain, which results in differences in calculated evaporation on rainy days. Monitoring networks with evaporation pans should have uniform instrumentation that accurately records rainfall into the pans for consistent results.     

ESTIMATING AVERAGE MONTHLY LAKE EVAPORATION IN THE NORTHEAST UNITED STATES1

ABSTRACT: A methodology to estimate the average monthly lake evaporation, E(τ), (month τ=1,12) for fresh water bodies located in the northeast United States is presented. The approach combines analysis of at‐site, lake‐specific vertical water temperature profile data and a previously developed regional air temperature based model approximation of the widely accepted modified Penman energy budget estimate of mean monthly potential evaporation, E_p(τ) (mm/day). The paper presents procedures to develop site‐specific estimates of E_p(τ) and to convert water temperature data to average monthly conductive heat flux, G(τ). With monthly estimates of G(τ), the average monthly potential evaporation, E_p(τ), is then convertible to estimates of the average monthly lake evaporation, E(τ). This new method permits a good estimate of site‐specific lake evaporation rates without the data and computational requirements of the Penman energy budget procedure nor the comparatively expensive, time consuming field eddy correlation approach.     

RELATIVE RATES OF EVAPORATIVE WATER LOSSES FROM OPEN AND VEGETATION COVERED WATER BODIES1

ABSTRACT: A review of literature pertaining to the relative rates of evaporation from vegetation covered and open water bodies is presented. The review indicates that the only reliable experiments capable of correctly addressing this question are those conducted in situ. Experiments of this nature show the ratio of vegetation covered (swamp) evaporation to open water evaporation to generally be less than unity over extensive surfaces and to only approach unity for vegetation that is young and vigorous. Recent experimental evidence presented within a theoretical context, however, indicates that even in the latter situation the ratio may never reach unity. Consequently, over large lakes and reservoirs, the presence of vegetation may actually be a water conservation mechanism, with the eradication of the vegetation leading to significantly increased evaporative water losses.     

MONTHLY RUNOFF PREDICTIONS BASED ON RAINFALL FORECASTS IN A SMALL OKLAHOMA WATERSHED1

ABSTRACT: Conditions under which monthly rainfall forecasts translate into monthly runoff predictions that could support water resources planning and management activities were investigated on a small watershed in central Oklahoma. Runoff response to rainfall forecasts was simulated using the hydrologic model SWAT. Eighteen scenarios were examined that represented combinations of wet, average, and dry antecedent rainfall conditions, with wet, normal, and dry forecasted rainfall. Results suggest that for the climatic and physiographic conditions under consideration, rainfall forecasts could offer potential application opportunities in surface water resources but only under certain conditions. Pronounced wet and dry antecedent rainfall conditions were shown to have greater impact on runoff than forecasts, particularly in the first month of a forecast period. Large forecast impacts on runoff occurred under wet antecedent conditions, when the fraction of forecasted rainfall contributing to runoff was greatest. Under dry antecedent conditions, most of the forecasted rainfall was absorbed in the soil profile, with little immediate runoff response. Persistent three‐month forecasts produced stronger impacts on runoff than one‐month forecasts due to cumulative effects in the hydrologic system. Runoff response to antecedent conditions and forecasts suggest a highly asymmetric utility function for rainfall forecasts, with greatest decision‐support potential for persistent wet forecasts under wet antecedent conditions when the forecast signal is least dampened by soil‐storage effects. Under average and dry antecedent conditions, rainfall forecasts showed little potential value for practical applications in surface water resources assessments.     

MULTIVARIATE TREND TESTING OF LAKE WATER QUALITY1

ABSTRACT: Multivariate methods of trend analysis offer the potential for higher power in detecting gradual water quality changes as compared to multiple applications of univariate tests. Simulation experiments were used to investigate the power advantages of multivariate methods for both linear model and Mann-Kendall based approaches. The experiments focused on quarterly observations of three water quality variables with no serial correlation and with several different intervariable correlation structures. The multivariate methods were generally more powerful than the univariate methods, offering the greatest advantage in situations where water quality variables were positively correlated with trends in opposing directions. For illustration, both the univariate and multivariate versions of the Mann-Kendall based tests were applied to case study data from several lakes in Maine and New York which have been sampled as part of EPA's long term monitoring study of acid precipitation effects.     

The origin and fate of arsenic in coalbed natural gas-produced water ponds

Coalbed natural gas (CBNG)-produced water contains small amounts of trace metals that can accumulate over time in produced water retention ponds. Within the Powder River Basin (PRB) of Wyoming, high concentrations of trace metals in pond water and their effect on shallow groundwater are potential concerns. A pond with a maximum As concentration of 146 microg L(-1) was studied in detail to determine the potential for groundwater pollution and to explain the cause for the high concentration of As. Infiltration characteristics, subsurface hydrology, our fall and pond water quality, isotope signatures, and trace metal balances were examined to assess the hydrology and geochemistry of the pond. The results indicated minimum or no infiltration of pond water and no measurable contamination of the shallow groundwater. The high As concentrations in the pond were determined to be the result of semi-continuous inputs of CBNG-produced water with low As concentrations (0.20-0.48 microg L(-1)), exasperated by low pond volumes during drought conditions. Because of reduced infiltration and high evaporation rates, As became concentrated over time. Reduced infiltration was most likely caused by the high sodium concentration and high sodium adsorption ratio of the CBNG-produced water, which disrupt soil structure. The findings for the pond and the techniques used may serve as a template for future impact assessments of other CBNG-produced water ponds and are relevant for the approximately 4000 ponds currently permitted in the PRB and for future ponds. Further studies are recommended in the use of playa landforms to store marginal-quality produced water.     

PULSED TRICKLING EFFECTS ON SOIL MOISTURE DISTRIBUTION1

ABSTRACT Laboratory experiments were conducted to study effects of trickle emitter discharge rate on the distribution of soil moisture in a silty-clay loam soil. Both pulsed and continuous irrigation treatments were studied. A simulation model was used to evaluate the results obtained in the laboratory. The agreement between the predicted and measured soil moisture distribution patterns was quite good. For both pulsed and continuous applications, increasing trickle discharge rate resulted in a decrease in the horizontal component and an increase in the vertical component of the wetted soil profile. Compared to the continuous treatments, pulsed applications resulted in significant reduction in water loss below the root zone. Pulsed applications rates can replace continuous small discharge rates to reduce irrigation water runoff problems on heavy soils and with restricted infiltration allow the use of larger emitter orifices to decrease potential clogging of the trickle system.     

MODELING PERCOLATION LOSSES FROM A PONDED FIELD UNDER VARIABLE WATER-TABLE CONDITIONS1

ABSTRACT: A numerical simulation model was developed to predict the vertical and lateral percolation losses from a ponded agricultural field. The two-dimensional steady-state unsaturated/ saturated flow equation was solved using the finite-difference technique. A constant ponding depth was maintained at the soil surface with different water table conditions in an application of the model for rice fields bordered by bunds. Field experiments were conducted for two different water table depths to collect data on the spatial distribution of volumetric soil-moisture content for model verification. The measured soil-moisture content values were found to be in close agreement with those predicted by the model. The sensitivity analysis of the model with selected hydrologic conditions shows that the model is most sensitive to the values of saturated hydraulic conductivity, but relatively less sensitive to water table depth, ponding depth, and evaporation rate from the soil surface. It implies that, in a ponded rice field condition, the lateral and vertical percolation losses are mostly governed by the hydraulic conductivity of the soil. The vertical percolation losses were almost equal to the saturated hydraulic conductivity values and, in most cases, these losses increased with deeper water table depths. The lateral percolation losses also increased with deeper water table depths; however, these losses were relatively small in comparison to the vertical percolation losses. The vertical and lateral percolation losses increased with the increase in ponding depths. The lateral percolation losses through the bund decreased when the evaporation losses increased from the soil surface. The results of this study indicate that the percolation losses from a ponded field may be predicted accurately for a wide range of soil and hydrological conditions when the values of hydraulic conductivity, evaporation rate, depth of ponding, and water table depth are accurately known.     

APPROACHES TO MULTIVARIATE MODELING OF WATER RESOURCES TIME SERIES1

ABSTRACT: Alternative approaches suggested for modeling multiseries of water resources systems are reviewed and compared. Most approaches fall within the general framework of multivariate ARMA models. Formal modeling procedures suggest a three-stage iterative process, namely: model identification, parameter estimation and diagnostic checks. Although a number of statistical tools are already available to follow such modeling process, in general, it is not an easy task, especially if high order vector ARMA models are used. However, simpler ARMA models such as the contemporaneous and the transfer-function models may be sufficient for most applications in water resources. Two examples of modeling bivariate and trivariate streamflow series are included. Alternative modeling procedures are used and compared by using data generation techniques. The results obtained suggest that low order models, as well as contemporaneous ARMA models, reproduce quite well the main statistical characteristics of the time series analyzed. It is assumed that the same conclusions apply for most water resources time series.     

HYDROLOGIC BUDGET FOR A FRESHWATER MARSH IN FLORIDA1

ABSTRACT: Accurate water balance calculations are essential for water resource and environmental management decisions, but many of the terms used in the equation are difficult to measure. In this study, a method for measuring rates of evapotranspiration and net seepage from a freshwater marsh in southwest Florida is described. The results are compared to evaporation pan estimates as well as to calculations that balanced all the terms in the hydrologic budget. The measured rates of evapotranspiration showed a. distinct seasonal trend ranging from an average high of 0.24 in/d during July 1992 to a low of 0.06 in/d in January 1993. Evapotranspiration rates were higher than Class A evaporation pan measurements during July and August, indicating transpiration by plants exceeded evaporation by pans. Net ground water seepage flowed out of the marsh except during periods of high water table conditions. When all terms in the hydrologic budget were evaluated, the equation balanced on a yearly basis with an error of 2 percent, on a seasonal basis with errors less than 7 percent, but on a monthly basis errors were as great as 30 percent. Total annual rainfall on the marsh was 45 percent of the total marsh hydrologic input and was approximately equal to the loss by evapotranspiration of 41 percent.     

区域水资源安全评价——以四川省内江市为例

运用AHP法建立了区域水资源安全评价指标体系,以四川省内江市为例,提出了符合当地资源现状的评价标准,并对其水资源安全状况进行评估。结果表明,内江市水资源安全存在潜在威胁,供水安全问题不容忽视。其中心城区水资源安全问题尤为突出,其他区域处于顸警状态,据此,对内江市水资源管理和保护提出了建议。     

Mechanistic Simulation of Tree Effects in an Urban Water Balance Model1

Abstract: A semidistributed, physical‐based Urban Forest Effects – Hydrology (UFORE‐Hydro) model was created to simulate and study tree effects on urban hydrology and guide management of urban runoff at the catchment scale. The model simulates hydrological processes of precipitation, interception, evaporation, infiltration, and runoff using data inputs of weather, elevation, and land cover along with nine channel, soil, and vegetation parameters. Weather data are pre‐processed by UFORE using Penman‐Monteith equations to provide potential evaporation terms for open water and vegetation. Canopy interception algorithms modified established routines to better account for variable density urban trees, short vegetation, and seasonal growth phenology. Actual evaporation algorithms allocate potential energy between leaf surface storage and transpiration from soil storage. Infiltration algorithms use a variable rain rate Green‐Ampt formulation and handle both infiltration excess and saturation excess ponding and runoff. Stream discharge is the sum of surface runoff and TOPMODEL‐based subsurface flow equations. Automated calibration routines that use observed discharge has been coupled to the model. Once calibrated, the model can examine how alternative tree management schemes impact urban runoff. UFORE‐Hydro model testing in the urban Dead Run catchment of Baltimore, Maryland, illustrated how trees significantly reduce runoff for low intensity and short duration precipitation events.     

Differences in Evaporation Between a Floating Pan and Class A Pan on Land1

Abstract: Research was conducted to develop a method for obtaining floating pan evaporation rates in a small (less than 10,000 m²) wetland, lagoon, or pond. Floating pan and land pan evaporation data were collected from March 1 to August 31, 2005, at a small natural wetland located in the alluvium of the Canadian River near Norman, Oklahoma, at the U.S. Geological Survey Norman Landfill Toxic Substances Hydrology Research Site. Floating pan evaporation rates were compared with evaporation rates from a nearby standard Class A evaporation pan on land. Floating pan evaporation rates were significantly less than land pan evaporation rates for the entire period and on a monthly basis. Results indicated that the use of a floating evaporation pan in a small free‐water surface better simulates actual physical conditions on the water surface that control evaporation. Floating pan to land pan ratios were 0.82 for March, 0.87 for April, 0.85 for May, 0.85 for June, 0.79 for July, and 0.69 for August.     

ESTIMATING EVAPORATION FROM UTAH'S GREAT SALT LAKE USING THERMAL INFRARED SATELLITE IMAGERY1

ABSTRACT: Water surface temperatures can be obtained from satellite thermal remote sensing. Landsat and other satellites sense emitted thermal infrared radiation on a regular basis over much of the earth's surface. Evaporation is accomplished by the net transport of mass from the water surface to the atmosphere. The evaporative transfer predominantly determines the water surface temperature. Hence, there should be good correlations between evaporation and surface temperatures. Previous investigations on Utah Lake with satellite-derived temperatures and pan- and model-derived evaporation values have produced good correlations. However, more study was required with additional satellite data and evaporation measurements for saltwater conditions. The applicability of this method for estimating evaporation on Utah's Great Salt Lake was of particular interest at this time because of the unprecedented rise of this terminal lake. Satellite thermal data and evaporation data from four different years were obtained for the Great Salt Lake and the surrounding region. More than 350 correlation and linear regression analyses were performed on the temperature and evaporation data. The lake salt concentrations were also factored into the analyses in several different ways. The correlation results were generally very good and a methodology for using satellite-derived water surface temperatures along with salt concentrations was developed to estimate evaporation.     

Sorption studies of mixed chromium and chlorinated ethenes at the field and laboratory scales

The sorption and desorption behavior of hexavalent chromium and chlorinated ethenes in a sandy ground water aquifer with a low reduction capacity was evaluated by performing a variety of analyses and experiments at the laboratory (batch and column studies) and field (in situ injection-withdrawal experiment) scales. The partitioning coefficients determined from the field and laboratory experiments are generally similar. Both sets of experiments yielded relatively low partition coefficients for chromium and chlorinated ethenes. The column studies and injection-withdrawal experiment indicate that chromium has the potential to leach from aquifer sediments and act as a secondary source of contamination. However, the magnitude of the secondary source effect is not significant due to low concentrations of leachable contamination. The chromium sorption isotherm data were also simulated using the triple layer surface complexation model (TLM). The isotherm data were modeled using the TLM, illustrating the applicability of geochemical modeling for sorption of chromium to these sediments under variable pE-pH conditions.