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Understanding water flow and its relative quantities through different pathways is vital for watershed management. Like many problems in hydrology, numbers of methods have been proposed for streamflow partitioning. Five methods were identified as being the most relevant and least input intensive. This study tested performance of these methods against separately measured surface and subsurface flow data from the coastal plain physiographic region of the southeastern United States. Separately measured surface and subsurface flow were collected for 12 years (1970–1981) in a field scale watershed by the Southeast Watershed Research Laboratory of the USDA-Agricultural Research Service. Results of comparative analysis indicated that Method IV performed the best. Results also indicated that accuracy of this method is highly dependent upon the proper estimation of the “fraction coefficient” that is based on many physical and hydrologic characteristics of the watershed. This study concluded that deterministic/empirical methods such as Boughton’s Method IV, require proper parameter value for increased accuracy. [ABSTRACT FROM AUTHOR]

The infiltration models of Kostiakov, Green-Ampt, and Philip (two and three terms equations) were used, calibrated, and evaluated to simulate in-situ infiltration in nine different soil types. The Osborne-Moré modified version of the Levenberg-Marquardt optimization algorithm was coupled with the experimental data obtained by the double ring infiltrometers and the infiltration equations, to estimate the model parameters. Comparison of the model outputs with the experimental data indicates that the models can successfully describe cumulative infiltration in different soil types. However, since Kostiakov's equation fails to accurately simulate the infiltration rate as time approaches infinity, Philip's two-term equation, in some cases, produces negative values for the saturated hydraulic conductivity of soils, and the Green-Ampt model uses piston flow assumptions, we suggest using Philip's three-term equation to simulate infiltration and to estimate the saturated hydraulic conductivity of soils. [ABSTRACT FROM AUTHOR]

This hypothesis-generating study explores spatial patterns of childhood cancers in Maryland and investigates their potential associations with herbicides and nitrates in groundwater. The Maryland Cancer Registry (MCR) provided data for bone and brain cancers, leukemia, and lymphoma, for ages 0–17, during the years 1992–1998. Cancer clusters and relative risks generated in the study indicate higher relative risk areas and potential clusters in several counties. Contingency table analysis indicates a potential association with several herbicides and nitrates. Cancer rates for the four types have a crude odds ratio (OR) = 1.10 (0.78–1.56) in relationship to atrazine, and an OR = 1.54 (1.14–2.07) for metolachlor. Potential association to mixtures of three compounds give an OR = 7.56 (4.16–13.73). A potential association is indicated between leukemia and nitrates, OR = 1.81 (1.35–2.42), and bone cancer with metolachlor, OR = 2.26 (0.97–5.24). These results give insight to generate a hypothesis of the potential association between exposure to these herbicides and nitrates and specific types of childhood cancer. [ABSTRACT FROM AUTHOR]

The Chemical, Runoff, Erosion from Agricultural Management Systems (CREAMS) model was used to simulate the long‐term relative effects of different agricultural best management practices (BMP's) on nitrogen losses to surface and groundwater systems. Soils, geology, climate, and cultural practices of watersheds representing coastal plain (Wye watershed), Piedmont (field A), and Appalachian (field E) physiographic regions in the Chesapeake Bay basin were selected for simulation purposes. Different tillage practices (conventional till and no‐till) with and without erosion control structures, with and without a nutrient management plan, and with and without winter cover were selected for the purpose of this study. The results showed that a nutrient management plan (NMP) plays a major role in reducing surface and groundwater loadings of nitrogen. Although different practices were identified as being best or worst case scenarios with respect to surface and ground‐water loadings, respectively, closer examination and overall ranking revealed no‐till (NT) with NMP to be the optimum BMP studied in both the Piedmont and Appalachian regions. It was also found that winter cover results in significant reductions in N losses to surface and ground‐water systems in the coastal plain physiographic region. This study suggests that ranking and selecting the proper BMP should be based on its impact on both surface and groundwater quality rather than on a single resource. This is especially important considering the fact that both human and other living resources use both surface and groundwater for drinking or habitual environment. [ABSTRACT FROM PUBLISHER]

Evaluating the relative amounts of water moving through the different components of the hydrological cycle is required for precise management and planning of water resources. An important aspect of this evaluation is the partitioning of streamflow into surface (quick flow) and base-flow components. A prior study evaluated 40 different approaches for hydrograph-partitioning on a field scale watershed in the Coastal Plain of the Southeastern United States and concluded that the Boughton's method produced the most consistent and accurate results. However, its accuracy depends upon the proper estimation of: (1) the end of surface runoff, and (2) the fraction factor (α) that is function of many physical and hydrologic characteristics of a watershed. Proper identification of the end of surface runoff was accomplished by using a second derivative approach. Applying this approach to 12 years of separately measured surface and subsurface flow data from a field scale watershed (study area) proved to be accurate for 87% of the time. Estimation of the α value was accomplished in this study using two steps: (1) alpha was fitted to individual hydrographs: and, (2) a regression equation that determines these alpha values based on climatological factors (e.g., rainfall, evapotranspiration) was developed. Using these strategies improved the streamflow partitioning method's performance significantly. [ABSTRACT FROM AUTHOR]

A decision support system in the framework of the geographic information system (GIS) and subsurface flow model, Hydrosub, were used to identify critical areas from simulated spatial distributions of relative nitrogen export. Diagnosis and prescription Expert Systems (ES) are developed and applied to the identification of probable causes of excessive nitrogen export and selection of appropriate Best Management Practices (BMPs). The result is a spatially distributed set of recommended Best Management Practices that are feasible economically and environmentally. For the study watershed, using catch crops and rhizobium-legume (instead of using conventional commercial fertilizers) were the most recommended Best Management Practices. [ABSTRACT FROM AUTHOR]

Atrazine transport through packed 10 cm soil columns representative of the 0–10 cm soil horizon was observed by measuring the atrazine recovery in the total leachate volume, and upper and lower soil layers following infiltration of 7.5 cm water using a mechanical vacuum extractor (MVE). Measured recoveries were analyzed to understand the influence of infiltration rate and delay time on atrazine transport and distribution in the column. Four time periods (0.28, 0.8, 1.8, and 5.5 h) representing very high to moderate infiltration rates (26.8, 9.4, 4.2, and 1.4 cm/h) were used. Replicate soil columns were tested immediately and following a 2-d delay after atrazine application. Results indicate atrazine recovery in leachate was independent of infiltration rate, but significantly lower for infiltration following a 2-d delay. Atrazine distribution in the 0–1 and 9–10 cm soil layers was affected by both infiltration rate and delay. These results are in contrast with previous field and laboratory studies that suggest that atrazine recovery in the leachate increases with increasing infiltration rate. It appears that the difference in atrazine recovery measured using the MVE and other leaching experiments using intact soil cores from this field site and the rain simulation equipment probably illustrates the effect of infiltrating water interacting with the atrazine present on the soil surface. This work suggests that atrazine mobilization from the soil surface is also dependent on interactions of the infiltrating water with the soil surface, in addition to the rate of infiltration through the surface soil. [Copyright &y& Elsevier]

• This manuscript provides a planning tool for reclaimed water use in agriculture to alleviate pressure on freshwater sources. • A GIS-MCDA framework was developed to produce the agricultural land suitability maps for irrigation with reclaimed water. • Multiple qualitative and quantitative decision criteria were included in the developed GIS-MCDA. • The developed decision framework was tested at a large scale (State of California) with multiple crop patterns. • Proximity to reclaimed water source and crop type were the most influential criteria for irrigation with reclaimed water. Water scarcity, climate variability and continuing growth in water demand have put severe pressure on high‐quality freshwater sources. This challenge exacts the necessity to explore alternative water sources for agricultural irrigation. The objective of this study was to implement the integrated geospatial Multi-Criteria Decision Analysis (MCDA) with the Analytical Hierarchy Process (AHP) to evaluate the potentiality of reclaimed water use for agricultural irrigation in California. Five evaluation criteria included in this study were agricultural land (crop type), climate conditions, water policies, irrigation status, and proximity to wastewater treatment plants (WWTPs) respectively. The suitability maps for reclaimed water use were generated for three cases in terms of accessibility to WWTPs, their discharge volume and appropriate treatment processes respectively. In addition, a composite suitability map was produced using the hybrid model considering all three cases together. Results from this study led to a better understanding of sustainable reclaimed water use for crop irrigation at a regional level. It provided supporting evidence of the applicability of the GIS-MCDA method integrated with AHP technique for a larger geographical scale with a diverse crop pattern. This study established the importance of using both knowledge-based and data-driven criteria and sub-criteria in the decision framework. The results also highlighted how the spatial distribution of suitable areas for reclaimed water reuse is closely linked to the agricultural areas. [ABSTRACT FROM AUTHOR]

Stormwater green infrastructure (GI) practices are implemented in urban watersheds to control stormwater runoff, reduce pollution, and adapt to climate change. This study evaluated the robustness of a watershed with stormwater GI and a watershed with traditional stormwater controls in Clarksburg, Maryland, to future climate change. The USDA Soil and Water Assessment Tool (SWAT) was calibrated to USGS daily streamflow data from 2011 to 2016 to evaluate watershed-scale daily and seasonal runoff responses to multiple future climate and management scenarios. The stormwater GI watershed had less runoff than the traditional management watershed in climate change scenarios for most days with rainfall (>98% of days). However, the climate change scenarios resulted in increased seasonal fall and winter runoff compared to current conditions in both watersheds. Simulated expansion of GI implementation reduced runoff in both watersheds under future climate scenarios. This study assesses climate robustness of existing stormwater GI at a watershed scale and confirms previous evaluations of hypothetical stormwater GI effectiveness for adapting watersheds to climate change. [ABSTRACT FROM AUTHOR]

To reduce nutrient pollution in urban watersheds, residents need to voluntarily practice a range of stormwater Best Management Practices (BMPs). However, little is known about the underlying social factors that may act as barriers to BMP implementation. The overall goal of this study was to better understand barriers to BMP implementation by exploring the links among resident demographics, knowledge, and behaviors so that appropriate education can be more effectively developed and targeted. In 2014–2015, a detailed questionnaire was administered door-to-door to 299 randomly selected households in two sub-watersheds of the Chesapeake Bay basin to test relationships among resident demographics, knowledge and attitudes towards water resources and BMPs, and BMP implementation. Multifactor regression models showed that respondents who had greater knowledge of water resources and BMPs lived in households that implemented greater numbers of BMPs. In turn, resident BMP knowledge, or familiarity with BMPs, strongly varied with race and ownership status, with respondents who identified as Caucasian or within a collection of ‘Other’ races, and who were home owners, having greater BMP knowledge than respondents who identified as African American and who were home renters, respectively. Renters and members of homeowner’s associations were also less likely to implement BMPs independent of knowledge, possibly reflecting perceived or real bureaucratic or procedural barriers to good stormwater management. Overall, respondents preferred to receive educational materials on stormwater via pamphlets and YouTube videos. These results suggest that resident ownership status knowledge is important to determining the number of household BMPs, and that education outreach should probably target African American and renting households that have lower BMP knowledge and landlords and administrators of homeowner’s associations using well-planned print and video educational media. [ABSTRACT FROM AUTHOR]

In urbanized areas, incorporating residents’ concerns and priorities into the stormwater management debate has focused on adults rather than youth. This study used Photovoice, a tool that includes photographs taken by youth, to uncover youth concerns and perceptions about their local watersheds. This study consisted of a comparative study of two watersheds. Twenty students produced 468 photographs. Although both groups of students shared common themes regarding stormwater and pollution, these themes differed in level of concerns over local environmental issues, sentiments with particular features in their local watersheds, and concerns about local watersheds. From a methodological perspective, Photovoice provided a way of capturing youth perspectives and to identify important features and issues in their respective local watersheds. [ABSTRACT FROM PUBLISHER]

Over the last two centuries, the impact of the Human System has grown dramatically, becoming strongly dominant within the Earth System in many different ways. Consumption, inequality, and population have increased extremely fast, especially since about 1950, threatening to overwhelm the many critical functions and ecosystems of the Earth System. Changes in the Earth System, in turn, have important feedback effects on the Human System, with costly and potentially serious consequences. However, current models do not incorporate these critical feedbacks. We argue that in order to understand the dynamics of either system, Earth SystemModels must be coupled with Human SystemModels through bidirectional couplings representing the positive, negative, and delayed feedbacks that exist in the real systems. In particular, key Human System variables, such as demographics, inequality, economic growth, and migration, are not coupled with the Earth System but are instead driven by exogenous estimates, such as United Nations population projections.This makes current models likely to miss important feedbacks in the real Earth-Human system, especially those that may result in unexpected or counterintuitive outcomes, and thus requiring different policy interventions from current models.The importance and imminence of sustainability challenges, the dominant role of the Human System in the Earth System, and the essential roles the Earth System plays for the Human System, all call for collaboration of natural scientists, social scientists, and engineers in multidisciplinary research and modeling to develop coupled Earth-Human system models for devising effective science-based policies and measures to benefit current and future generations. [ABSTRACT FROM AUTHOR]

Vegetated filter strips (VFS) are commonly recommended as a best management practice to prevent manure-borne microorganisms from reaching surface water resources. However, relatively little is known about the efficacy of VFS in mitigating bacterial runoff from land-applied swine manure. A field lysimeter study was designed to evaluate the effect of surface soil hydrologic conditions and vegetation on the retention of swine manure-borne Escherichia coli and Salmonella under simulated rainfall conditions. Experimental plots (6.5 m × 3.9 m) were set on a 5% slope lysimeter with loamy topsoil, clay loam or loam subsoil and a controllable groundwater level. Three small flow-intercepting miniflumes were installed 4.5 m from the plot's top, while all remaining runoff was collected in a gutter at the bottom. Plots were divided into bare soil and grass vegetation and upper surface soil moisture before rainfall events was controlled by the subsurface groundwater level. Swine manure slurry inoculated with E. coli and Salmonella, and with added bromide tracer, was applied on the top of the plots and simultaneously initiated the simulated rainfall. Runoff was collected and analyzed every 5 min. No substantial differences between retention of E. coli and Salmonella were found. In initially wet soil surface conditions, there was limited infiltration both in bare and in vegetated plots; almost all bromide and about 30% of bacteria were recovered in runoff water. In initially dry soil surface conditions, there were substantial discrepancies between bare and vegetated plots. In bare plots, recoveries of runoff water, bromide and bacteria under dry conditions were comparable to wet conditions. However, in dry vegetated plots, from 50% to 75% of water was lost to infiltration, while bromide recoveries ranged from 14 to 36% and bacteria recovery was only 5%. Substantial intraplot heterogeneity was revealed by the data from miniflumes. GIS analysis of the plot microtopography showed that miniflumes located in the zones of flow convergence collected the majority of bacteria. Overall, the efficiency of VFS, with respect to the retention of swine manure bacteria, varied dramatically depending upon the hydrologic soil surface condition. Consequently, VFS recommendations should account for expected amounts of surface soil water saturation as well as the relative soil water storage capacity of the VFS. [Copyright &y& Elsevier]