EFFECTS OF PRECIPITATION AND LAND USE ON STORM RUNOFF1

ABSTRACT: Storm-runoff quantity and quality were studied in three watersheds located near St. Paul in Ramsey County, Minnesota, from April 15 through September 15 of 1984, 1985, and 1986 to qualitatively determine the effects of precipitation and selected land uses on storm runoff. In respect to precipitation effects, differences in stormrunoff quantity between years in an urban watershed that lacks wetlands appear to be related to the average storm size (amount of precipitation) during the study period of each year. In contrast, the differences in storm-runoff quantity from watersheds that contain wetlands appear to be related to total precipitation during study period of each year. In respect to land use, the differences in storm-runoff quantity appear to be related to the amounts of impervious and wetland area. The watershed that contains the largest amount of impervious area and smallest amount of wetland area has the largest amount of storm runoff. Differences in storm-runoff quality appear to be related to the amounts of wetland and lake area. The watershed that contains the largest amounts of wetland and lake area has the smallest storm-runoff loading of suspended solids, phosphorus, and nitrogen. The wetland and lake areas likely retain the loading and, subsequently, lower the amount of storm-runoff loading exported from a watershed.     

A PRELIMINARY STUDY OF THE EFFECTS OF DRAINAGE AND HARVESTING ON WATER QUALITY IN OMBROTROPHIC BOGS NEAR SEPT-ILES,QUEBEC1

ABSTRACT: Runoff and ground-water samples were collected from four ombrotrophic bogs, representing undisturbed and drained/harvested conditions, at two-week intervals during the summer of 1984. Analyses of samples for water quality parameters revealed significant (P < 0.05 level) increases in specific conductance, NH4⁺-N, total dissolved P, Mg, K, and Na and a decrease in the E₄:E₆ ratio (suggesting increased proportions of humic acid) associated with drainage. There were no significant changes in dissolved organic carbon, Ca concentrations, or pH. Comparison of samples collected before, during, and after ditching showed increases in the dissolved organic carbon, NH₄⁺-N, total dissolved P, K, and Na and a decrease in the E₄:E₆ ratio, but these changes were short lived; water quality returned to preditching values after about a week. The observed changes in water quality are small, probably because the peat is very acid (pH 3.0 to 4.5).     

ESTABLISHING PRIORITIES FOR WETLAND MANAGEMENT1

Wetlands provide a variety of ecological services, but are attractive sites for many development activities. Between the mid-1950's and mid-1970's about 550,000 acres, or about 0.5 percent, of the vegetated wetlands remaining in the conterminous states were converted to other uses each year. About 80 percent of these losses involved draining and clearing of inland wetlands for agricultural purposes. Recent reductions in national wetland conversion rates are due primarily to declining rates of agricultural drainage and secondarily to government programs that regulate wetlands use. Several governmental policies and programs exist that either encourage or discourage wetland conversions. Section 404 of the Clean Water Act is the major tool for Federal involvement in controlling the conversion of wetlands to other uses. The 404 program, in combination with State regulatory programs, is responsible for reducing annual conversions nationwide by about 50 percent of what is applied for, or 50,000 acres of wetlands per year, primarily through project modifications. Coastal wetlands are reasonably well protected. Inland, freshwater wetlands are generally poorly protected. Efforts to protect wetlands, given a set level of resources, could be improved by categorizing wetlands according to their relative importance and focusing existing wetland programs on high value wetlands.     

An assessment of urban development into coastal wetlands using historical aerial photography: a case study

Like many other states in the USA, Virginia passed legislation to protect coastal wetlands with limited information on the rate and location of past wetlands conversions. This information, however, can be useful in the design of cost-effective and flexible programs for wetlands management, particularly when such information is used in combination with studies of the socioeconomic value of wetlands. This paper reports on the use of photogrammetric and interpretive methods to determine historical changes in wetlands use for Virginia Beach and Accomack counties, Virginia. Conclusions are drawn as to the use of such information in policy design and program monitoring.     

A FRAMEWORK FOR PHOSPHORUS TRANSPORT MODELING IN THE LAKE OKEECHOBEE WATERSHED1

ABSTRACT: A modeling framework was developed to determine phosphorus loadings to Lake Okeechobee from watersheds located north of the lake. This framework consists of the land-based model CREAMS-WT, the in-stream transport model QUAL2E, and an interface procedure to format the land-based model output for use by the in-stream model. QUAL2E hydraulics and water quality routines were modified to account for flow routing and phosphorus retention in both wetlands and stream channels. Phosphorus loadings obtained from previous applications of CREAMS-WT were used by QUAL2E, and calibration and verification showed that QUAL2E accurately simulated seasonal and annual phosphorus loadings from a watershed. Sensitivity and uncertainty analyses indicated that the accuracy of monthly loadings can be improved by using better estimates of in-stream phosphorus decay rates, ground water phosphorus concentrations, and runoff phosphorus concentrations as input to QUAL2E.     

进水方式对序批式深床人工湿地硝化效能的影响

针对现有人工湿地硝化效能低、占地面积大的问题,研究污水处理厂尾水人工湿地高效硝化深度处理技术,采用序批式深床人工湿地反应器(DSCW),考察进水方式及其运行工况对硝化效能的影响。结果表明,进水方式、进水时间和闲置时间对湿地硝化效能影响显著。进水方式采用"连续进水-间歇出水"较连续进出水运行工况NH_4~+-N去除率高39.69%。连续进水时间为5.5 h、7.5 h、11.5 h时,NH_4~+-N去除率分别为81.82%、88.12%、89.91%;闲置时间为0、2 h、4 h时,NH_4~+-N去除率分别为88.12%、94.46%、92.60%。反应器在水温(20±3)℃、负荷35.56 g NH_4~+-N/(m2·d)、连续进水7.5 h-间歇出水0.5 h-排空闲置2 h运行工况下,出水NH_4~+-N为0.91 mg/L,去除率为94.46%,系统NH_4~+-N去除效能大幅提高。     

以城市污水为水源和肥源对荒漠化土壤的修复效果

为了同步实现城市污水净化和荒漠化土壤修复,以荒漠化土壤(沙土)作为人工湿地基质(基质深度分别为0.1和0.6 m),分析不同运行条件(植物种类、水力负荷、基质深度、季节变化等)下湿地对净化城市污水、修复荒漠化土壤的效果. 结果表明:经过2 a的修复,城市污水中污染物作为荒漠化修复的肥源可以快速富集到荒漠化土壤中. 与原沙相比,沙土中w(有机质)、w(TN)、w(碱解氮)、w(TP)、w(速效磷)及电导率均极显著增加(P<0.01),而pH并无显著变化(P>0.05). 沙土容重极显著降低(P<0.01),孔隙率极显著增大(P<0.01). 当城市污水作为荒漠化土壤修复水源时,即使水力负荷低至0.0075 m3/(m2·d),植物仍能正常生长. 基质深度为0.1 m的潜流湿地在不同水力负荷时对污水中COD_Cr、TN、TP的最低平均去除率分别为59.46%、77.45%、62.36%;基质深度为0.6 m的潜流湿地对污水中三者的平均去除率分别为59.24%、32.02%、57.89%;基质深度为0.6 m的表面流湿地对污水中三者的平均去除率则分别为80.40%、14.00%、29.31%. 研究显示,以城市污水为水源和肥源对荒漠化土壤修复2 a后,沙土中养分含量均显著增加,沙土结构也得到明显改善,各湿地在夏秋季对污水中COD_Cr、TN、TP均有较好的去除效果.      

河口潮滩湿地CH4、CO2排放通量对氮硫负荷增强的响应

以闽江河口区高、中潮滩短叶茳芏湿地为研究对象,于2014年6—11月植物生长季进行氮硫负荷增强实验,利用静态箱-气象色谱法测定土壤CH_4、CO_2排放通量,并同步观测相关环境因子.结果表明,氮硫负荷增强对潮滩湿地CH_4、CO_2排放通量的影响不尽一致.与对照相比,NH_4~+-N输入使高、中潮滩CH4排放通量分别提高了(107.53%,7.19%),使高潮滩CO_2排放通量增加了3.39%,中潮滩减少了3.00%;NO_3~--N输入使高潮滩CH4、CO_2排放通量分别增加了(29.99%,16.99%),使中潮滩分别减少了(3.45%,4.77%);SO_4~(2-)-S输入使高、中潮滩CH4排放通量分别减少了(8.99%,7.67%),使高潮滩CO_2排放通量减少了3.87%,中潮滩增加了5.44%;N-S复合输入使高、中潮滩CH4排放通量分别提高了(72.48%,25.66%),CO_2排放通量提高了(13.32%,13.48%).氮硫负荷增强改变了短叶茳芏沼泽生长季CH_4、CO_2排放通量变化规律,但除了NH+4-N处理对高潮滩CH4通量的影响显著外,其他处理影响均未达到显著性水平.相关分析显示,高、中潮滩湿地CH_4、CO_2排放通量与土壤温度,含水率具有显著的正线性相关关系,与土壤电导率相关性不显著.在全球环境问题日益严重背景下,系统研究湿地生态系统温室气体排放的机制与规律,对于准确估算全球温室气体排放量具有重要而直接的意义.     

Hydrological,Physical, and Chemical Functions and Connectivity of Non‐Floodplain Wetlands to Downstream Waters: A Review

We reviewed the scientific literature on non‐floodplain wetlands (NFWs), freshwater wetlands typically located distal to riparian and floodplain systems, to determine hydrological, physical, and chemical functioning and stream and river network connectivity. We assayed the literature for source, sink, lag, and transformation functions, as well as factors affecting connectivity. We determined NFWs are important landscape components, hydrologically, physically, and chemically affecting downstream aquatic systems. NFWs are hydrologic and chemical sources for other waters, hydrologically connecting across long distances and contributing compounds such as methylated mercury and dissolved organic matter. NFWs reduced flood peaks and maintained baseflows in stream and river networks through hydrologic lag and sink functions, and sequestered or assimilated substantial nutrient inputs through chemical sink and transformative functions. Landscape‐scale connectivity of NFWs affects water and material fluxes to downstream river networks, substantially modifying the characteristics and function of downstream waters. Many factors determine the effects of NFW hydrological, physical, and chemical functions on downstream systems, and additional research quantifying these factors and impacts is warranted. We conclude NFWs are hydrologically, chemically, and physically interconnected with stream and river networks though this connectivity varies in frequency, duration, magnitude, and timing.     

Public Preferences for Compensatory Mitigation of Salt Marsh Losses: a Contingent Choice of Alternatives

Abstract:  Human activities continue to eliminate or degrade wetlands that provide rich habitat for many species. Compensatory mitigation, including creation of new wetlands, restoration of previously degraded wetlands, or preservation of existing wetlands, is one policy option that seeks to maintain no net loss of wetland habitat. Public support of wetland mitigation is essential because the public incurs the cost for many mitigation projects in the form of higher taxes. Therefore, public preferences should be considered when decisions are made about wetland mitigation options. We used a contingent-choice survey in Rhode Island to identify factors affecting public support for different types of compensatory wetland mitigation. Results were based on 640 survey responses. The amount of wetland lost during the original development project had no significant effect on the preferred mitigation alternative. Preferences for preservation, restoration, and no-action alternatives varied according to respondents' gender, education, and income. Certain general considerations applied, however, regardless of mitigation type. Respondents were willing to incur increases in taxes and fees for most mitigation projects. The larger the mitigation project and the lower the cost, the more likely it was to gain public support. The presence of endangered species contributed to public support, but less significantly than public access. Public access can be critical to public support, particularly if the size of the wetland is small or the cost is high. If the cost of providing public access, such as a boardwalk or viewing tower, is relatively small, the gain in public support for mitigation expenditures may well allow a substantial expansion of the area involved in mitigation projects and thus a greater increase in the amount of habitat conservation.