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Surface runoff

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  • The Water Erosion Prediction Project (WEPP) model and the Agricultural Non-Point-Source Pollution Model (AGNPS) were used in conjunction with a geographic information system (GIS) database to predict runoff and sediment discharges for Rock Creek watershed, an agricultural watershed in Ohio, USA.

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  • The same amount of water has been present on our planet for about 4 billion years, since shortly after the Earth was formed. Since then it has cycled through evaporation, condensation, precipitation and surface runoff multiple times. Water scarcity as an abiotic factor ranging from moderate to severe stress levels, accompanied by loss of moisture in the soil, is extremely hard for most organisms to cope with, particularly terrestrial plants and their food-chain dependents.

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  • Carmago et al. (1992) found that the rivers nearer industrial discharge point have adverse impact to the environment as well as to macrobenthic communities. Toxic contaminants from surface runoff, sewage discharges and industrial discharge have caused negative impacts towards the freshwater macrobenthic communities. The presence of substance chemical such as ammonia, chlorine, cyanide, metals, PCBs, pesticides and phenols would caused a decline pattern on the number of species and changes in the species composition.

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  • Preconstruction planning should be used to sequence major grading activities to minimize the exposure time of graded or denuded areas. The erosion prevention and sediment control measures and/or plans shall be modified as necessary so that they are effective at all times throughout the course of the project. The Operator will be responsible for the implementation and execution of all storm water runoff controls.

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  • In 1972, the Clean Water Act (CWA) delineated the basic structure for regulating discharges of pollutants into waters and for establishing quality standards for surface waters under the authority of EPA [10]. Under the CWA’s National Pollutant Discharge Elimination System program, stormwater permits were required for sediment runoff from construction sites and discharges of pollutants into surface waters [11]. The permitting system requires adoption of technology-based and water quality-based effluent limits [11,12].

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  • If the soil becomes saturated, oxygen may become scarce and in anoxic conditions, denitrifying bacteria may convert the nitrate to nitrogen gases (NO, N2O, and N2). Nitrogen converted to these gases becomes unavailable for plant uptake or for surface water contamination. Additionally, saturated soil during the growing season is harmful to many crops like maize that cannot tolerate low oxygen concentrations in the root zone for more than a few days.

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  • Diverse human-produced organic chemicals can enter surface and groundwater through human activities, including pesticide use and industrial processes, and as breakdown products of other chemicals (Carr and Neary 2008). Many of these pollutants, including pesticides and other non-metallic toxins, are used globally, persist in the environment, and can be transported long ranges to regions where they have never been produced (UNEP 2009).

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  • Variation in precipitation will also affect the salinity levels of surface water. Increased rainfall or runoff will likely reduce salinity levels, especially in winter, while lower precipitation levels and higher temperatures during summertime could increase salinity levels (Jacobs et al. 2001). As a result, semi- arid regions that suffer from decreasing runoff will be greatly impacted by salinization (Jacobs et al. 2001).

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  • In addition to the creation of more wastewater, urban areas add to poor water quality in a number of ways. The high concentration of impervious surfaces increases runoff from roads and can carry numerous pollutants such as oils, heavy metals, rubber, and other automobile pollution into waterways and streams. The reduction in water percolation into the ground can also affect the quantity and quality of groundwater. Stormwater runoff in urban areas can overwhelm combined stormwater and wastewater treatment systems when high volume flows exceed treatment capacities.

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  • Decreases in pH and ANC are often paral- leled by changes in element concentrations including increases in Al +3 concentrations and decreases in Ca +2 . High dissolved Al +3 concen- trations can have toxic effects on many types of aquatic biota, and at extreme levels few aquatic species can survive (Table 1). Organic forms of Al +3 are much less toxic than inorganic forms. Emerging research suggests that Ca +2 concentra- tions in streamwater are also an important bio- logical indicator.

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