Nutrient mitigation capacity in Mississippi Delta, USA drainage ditches

Eutrophication and hypoxia within aquatic systems are a serious international concern. Various management practices have been proposed to help alleviate nutrient loads transported to the Gulf of Mexico and other high-profile aquatic systems. The current study examined the nutrient mitigation capacity of a vegetated (V) and non-vegetated (NV) agricultural drainage ditch of similar size and landform in the Mississippi Delta. While no statistically significant differences in ammonium, nitrate, or dissolved inorganic phosphorus mitigation between the two ditches existed, there were significant differences in total inorganic phosphorus percent load reductions (V: 36% ± 4; NV: 71% ± 4). However, both agricultural drainage ditches were able to mitigate nutrients, thus reducing the load reaching downstream aquatic receiving systems. Further studies examining ecosystem dynamics within drainage ditches such as sediment and plant nutrient partitioning, as well as microbial processes involved, are needed to provide a better understanding of natural nutrient variability, seasonality and flux.     

Modeling transport and fate of nitrogen from urea applied to a near-trench paddy field

A simple but comprehensive model is developed to quantify N losses from urea applied to a near-trench paddy field, considering all the N-transformations such as urea hydrolysis, volatilization, nitrification, denitrification, and all the important transportations like runoff, lateral seepage, vertical leaching and crop uptake. Seasonal average data of field observations for three crop seasons were used for model calibration and validation, which showed that ammonia volatilization accounted for 26.5-29.4% of the applied N and N uptake by crop occupied 38.2-44.8%, while N losses via surface runoff, vertical leaching and lateral seepage varied from 5.6-7.7%, 4.0-4.9% to 5.0-5.3% of the applied N, respectively. These observed results were well predicted by our model, indicating that the model performed effectively at quantifying N losses via individual processes in a wide range of urea application rates and benefit for developing water and fertilizer management strategies for near-trench paddy fields.     

基于SWAT模型的松花江流域哈尔滨段径流量模拟

应用SWAT模型对朱顺屯—大顶子山断面(66 km)的松花江流域进行小区域径流模拟,选取2010—2013年的月实测数据进行参数的率定和验证,并对模型几个重要参数敏感性分析,总结参数取值变化对模拟结果的影响规律。结果表明:模拟结果的相对误差(Re)、相关系数(R2)和月径流模拟效率系数(Ens)分别为0.09、0.84、0.78,均在保证值范围内,说明SWAT模型适用于小范围流域内分布式水文模型的建立,对松花江哈尔滨段水文模型的建立具有指导作用。     

Hydroclimatic changes and drivers in the Sava River Catchment and comparison with Swedish catchments

In this study, we investigate long-term hydroclimatic changes and their possible relation to regional changes in climate, land-use and water-use over the twentieth century in the transboundary Sava River Catchment (SRC) in South Eastern Europe. In a hydropower dominated part of the SRC, unlike in an unregulated part, we find increase in average annual evapotranspiration and decrease in temporal runoff variability, which are not readily explainable by observed concurrent climate change in temperature and precipitation and may be more related to landscape-internal change drivers. Among the latter investigated here, results indicate hydropower developments as most closely related to the found hydroclimatic shifts, consistent with previous such indications in studies of Swedish hydropower catchments. Overall, the present results have quantitatively framed the recent history and present state of hydroclimate in the SRC, of relevance for water resources in several countries and for a majority of their populations. This provides a useful basis for further assessment of possible future hydroclimatic changes, under different scenarios of climate change and land/water-use developments in the region.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-015-0641-0) contains supplementary material, which is available to authorized users.     

Effects of cattle manure on erosion rates and runoff water pollution by faecal coliforms

The large quantities of slurry and manure that are produced annually in many areas in which cattle are raised could be an important source of organic matter and nutrients for agriculture. However, the benefits of waste recycling may be partially offset by the risk of water pollution associated with runoff from the fields to which slurry or manure has been applied. In this paper, the effects of cattle manure application on soil erosion rates and runoff and on surface water pollution by faecal coliforms are analysed. Rainfall simulations at a rate of 70 mm h(-1) were conducted in a sandy loam soil packed into soil flumes (2.5m long x 1m wide) at a bulk density of 1400 kg m(-3), with and without cattle slurry manure applied on the surface. For each simulation, sediment and runoff rates were analysed and in those simulations with applied slurry, presumptive faecal coliform (PFC) concentrations in the runoff were evaluated. The application of slurry on the soil surface appeared to have a protective effect on the soils, reducing soil detachment by up to 70% but increasing runoff volume by up to 30%. This practice implies an important source of pollution for surface waters especially if rainfall takes place within a short period after application. The concentrations of micro-organisms (presumptive faecal coliforms (PFCs)) found in water runoff ranged from 1.9 x 10(4) to 1.1 x 10(6) PFC 100mL(-1), depending on the initial concentration in the slurry, and they were particularly high during the first phases of the rainfall event. The result indicates a strong relationship between the faecal coliforms transported by runoff and the organic matter in the sediment.     

STEP WISE,MULTIPLE OBJECTIVE CALIBRATION OF A HYDROLOGIC MODEL FOR A SNOWMELT DOMINATED BASIN1

ABSTRACT: The ability to apply a hydrologic model to large numbers of basins for forecasting purposes requires a quick and effective calibration strategy. This paper presents a step wise, multiple objective, automated procedure for hydrologic model calibration. This procedure includes the sequential calibration of a model's simulation of solar radiation (SR), potential evapotranspiration (PET), water balance, and daily runoff. The procedure uses the Shuffled Complex Evolution global search algorithm to calibrate the U.S. Geological Survey's Precipitation Runoff Modeling System in the Yampa River basin of Colorado. This process assures that intermediate states of the model (SR and PET on a monthly mean basis), as well as the water balance and components of the daily hydrograph are simulated consistently with measured values.     

Prioritising catchment management projects to improve marine water quality

Runoff from human land-uses is one of the most significant threats to some coastal marine environments. Initiatives to reduce that runoff usually set runoff reduction targets but do not give guidance on how to prioritize the different options that exist to achieve them. This paper demonstrates an easy to interpret economic framework to prioritise investment for conservation projects that aim to reduce pollution of marine ecosystems caused by runoff from agricultural land-uses. We demonstrate how to apply this framework using data on project cost, benefit and feasibility with a subset of projects that have been funded to reduce runoff from subcatchments adjacent to the Great Barrier Reef. Our analysis provides a graphical overview of the cost-effectiveness of the investment options, enables transparent planning for different budgets, assesses the existence of trends in the cost-effectiveness of different categories, and can test if the results are robust under uncertainty in one or more of the parameters. The framework provided solutions that were up to 4 times more efficient than when omitting information on cost or benefit. The presented framework can be used as a benchmark for evaluating results from a range of prioritisation processes against the best possible conservation outcomes.     

坡度和雨强对喀斯特地区坡面产流产沙的影响

利用径流小区观测法,分析了坡度和雨强对贵州喀斯特地区4种地类坡面产流产沙的影响。结果表明,随坡度的增大,各地类坡面产流产沙量并没有表现出一致增大或减小的趋势,它们在很大程度上受土地利用方式和土壤类型的制约;随最大30 min雨强(I)的增大,坡面的产流产沙量增大。坡度为13°时,坡耕地在各地类中的产流产沙量最小,随坡度增大逐渐超过其他地类;除13°径流小区外,经济林地(梨树)在各种坡度、雨强范围内的产流产沙量均为各地类中最少;水保林地(香樟)在各种情况下的产流量虽较大,但产沙量相对较小;裸地在观测条件下的产流产沙量均较大。     

乌鲁木齐城市道路地面径流中重金属的污染特征分析

采用原子吸收光谱法,对乌鲁木齐市城区3个采样点的两次降雨过程中采集的路面径流进行了重金属Zn、Pb、Cd、Cu和Ni的含量分析.结果表明,道路径流中Zn、Pb、Cd污染较严重,但随着时间的推移,它们在雨水径流中的含量逐渐减少,符合"浓度初期冲刷"规律.     

Runoff water quality from manured riparian grasslands with contrasting drainage and simulated grazing pressure

Globally, management of grazed riparian areas is critically important to agricultural sustainability and environmental quality. However, the potential impacts of riparian grazing management on water quality are not well-documented, particularly in the southeastern USA. The objective of this work was to determine sediment and nutrient export under simulated rainfall from poorly drained and well-drained riparian soils where heavy or light grazing pressure by cattle was simulated. Plots were established on stands of existing vegetation to create grazing pressure treatments of (a) light-use (full ground cover, uncompacted), and with stands modified to establish (b) heavy-use (bare ground, compacted) treatments. Vegetation on poorly drained soils consisted of several typical wetland species (e.g., Pontederia cordata L., Juncus coriaceus Mackenzie) in the southeastern USA, whereas mixed tall fescue (Festuca arundinacea Schreb.)–dallisgrass (Paspalum dilatatum Poir.) stands were the dominant vegetation on well-drained soils. Runoff volume was generally greater from heavy-use than from light-use for poorly drained soils and for well-drained soils. Greater runoff volume was also observed from poorly drained soils compared to well-drained soils for both light-use and for heavy-use treatments. Light-use plots were remarkably effective at minimizing export of total suspended solids (TSS) on both soils (<30 kg ha⁻¹). Mean total Kjeldahl P (TKP) export was fourfold greater from heavy-use plots than from light-use plots on both soils. While export of nitrate-nitrogen (NO₃-N) was unaffected by grazing pressure and soil drainage, mean ammonium-nitrogen (NH₄-N) and total N (TN) export from poorly drained heavy-use plots was greater than fivefold that from well-drained light-use plots. Results indicate that livestock heavy-use areas in the riparian zone may export substantial TSS and nutrients, especially on poorly drained soils. However, when full ground cover is maintained on well-drained soils, TSS and nutrient losses may be limited.