Transformations and losses of fertilizer nitrogen on no-till and conventional till soils

A field study was conducted in 1982 to measure the effect of no-till (NT) and conventional till (CT) systems on N transformation after surface and subsurface applications of N fertilizers. Urea, urea-ammonium nitrate (UAN) solution, (NH₄)₂SO₄ (AS), and CA(NO₃)₂ were applied to NT and CT plots (5.95 m²) at a rate of 448 kg N ha^–1. A comparison of fertilizer N recovered in soils receiving incorporated or surface applied N was used to estimate NH₃ volatilization while denitrification was estimated from fertilizer N recovered in the presence and absence of nitrapyrin with incorporated N. Immobilization was assessed in microplots (0.37 m²) after surface application of (¹⁵NH₄)₂SO₄ to NT and CT systems at a rate of 220 kg N ha^–1.The results indicate little difference between NT and CT systems on urea hydrolysis rates and immobilization of surface applied fertilizer N. Approximately 50% and 10% of the surface applied N was recovered in the inorganic and organic fractions, respectively, on both tillage systems. The N not recovered was likely lost from plot areas through soil runoff. Incorporation of UAN, urea and AS resulted in 20 to 40% greater inorganic N recovery than from surface application. Nitrification rates were greater under the NT than the CT system. The similarities in concentration in the various N pools observed between the two tillage systems may be partially due to the short length of time that NT was imposed in this field study (<1 year) since other researchers using established tillage systems (>5 y) indicate that NT tends to promote decreased efficiency of fertilizer N.     

Stormwater runoff quality and quantity from asphalt, paver, and crushed stone driveways in Connecticut

This study compared the quality and quantity of stormwater runoff from replicated asphalt, permeable paver, and crushed-stone driveways. Rainfall was measured on-site and runoff was recorded using tipping buckets. Flow-weighted composite runoff samples were analyzed weekly for total suspended solids, total Kjeldahl nitrogen, nitrate-nitrogen, ammonia-nitrogen, total phosphorus (TP), zinc, lead, and copper. Infiltration rate was determined on each driveway annually. Repeated measures analysis of variance indicated that stormwater runoff was significantly different among each driveway type; the order of decreasing runoff was asphalt> paver> stone. Average infiltration rates were 0, 11.2 and 9.0 cm/h for asphalt, paver, and crushed stone driveways, respectively. Both paver and crushed stone driveways reduced stormwater runoff as compared to asphalt driveways. Runoff from paver driveways contained significantly lower concentrations of all pollutants measured than runoff from asphalt driveways. However, runoff from crushed stone driveways was similar in concentrations to runoff from asphalt driveways, except for TP concentrations, which were lower in runoff from crushed stone driveways than runoff from asphalt driveways. The mass export of measured pollutants followed the relative differences in stormwater runoff, rather than differences in concentrations.     

新型渗井-透水网格措施的径流调控效果研究

为更加合理地对雨水资源进行管理和调控,低影响开发(LID)措施日益成为我国许多城市"海绵化"的必然选择。透水网格被认为是一种有着良好雨洪管控效用的LID措施,然而大多情况下施工过程不尽规范,土基多采用渗透性不良的土质,这使得径流调控及渗流效益难以充分发挥,故拟以透水网格砖孔布设渗井来改善该现状。采用试验与SWMM仿真相结合的方法,研究了在6场重现期降雨作用下新型渗井-透水网格措施较透水网格在径流调控方面的改善效果,以及100年重现期降雨条件下两种措施的入渗规律。结果表明,在不同降雨场次下,新型措施较透水网格雨量径流系数降低了9.94%~51.09%,洪峰流量削减率提高了2.91%~30.42%;滞峰时间延迟效果不显著,在3 min以内;在100年重现期降雨下湿润锋迁移速率提高了73.47%。     

Modelling the impacts of climate change on surface runoff in small Mediterranean catchments: empirical evidence from Greece

During the last decades, a major factor that analysts and policy makers take into account in the assessment of the environment is climate change. This global physical process is expected to cause problems in natural and human environment. Thus, modelling climate change impacts may lead to prevention policies to minimize the degradation of life quality because of lack of water resources in the future. This study implicates Geographical Information System (GIS) and hydrological modelling tools to various scenarios of climate change such as the increase of temperature the decrease of rainfall, or even both of them, to estimate the potential impact of climate change on surface runoff in a typical catchment in Andros Island, Greece. Primary results indicate a proportional runoff decrease in the next 50 years because of global climate changes.     

Simulating the effects of climate change,economic and urban planning scenarios on urban runoff patterns of a metropolitan region

Urban development and climate change are expected to have significant effects on urban stormwater runoff. In this study, the Dynamic Urban Water Simulation Model (DUWSiM) is applied to Dublin, Ireland, to explore urban runoff patterns under varying urban growth and climate scenarios. Results show that annual urban runoff could decrease by 3.0% from climate change and monthly runoff could increase by 30% in winter and decrease by 28% in summer. Results also indicate that urban growth could increase annual runoff by up to 15%. The combined effect of climatic and land-use change generated runoff may potentially increase annual totals from between 2.9% to 21%. Monthly changes in runoff totals could increase by up to 57%. Accommodating these variations in runoff between the scenarios, flexible decentralised systems such as green roofs and pervious pavements, have a vital role in increasing the adaptability and long term sustainability of water infrastructure.     

Sediment and discharge yields within a minimally disturbed,headwater watershed in North Central Pennsylvania,USA, with an emphasis on Superstorm Sandy

We estimated discharge and suspended sediment (SS) yield in a minimally disturbed watershed in North Central Pennsylvania, USA, and compared a typical storm (September storm, 4.80 cm) to a large storm (Superstorm Sandy, 7.47 cm rainfall). Depending on branch, Sandy contributed 9.7–19.9 times more discharge and 11.5–37.4 times more SS than the September storm. During the September storm, the upper two branches accounted for 60.6% of discharge and 88.8% of SS at Lower Branch; during Sandy these percentages dropped to 36.1% for discharge and 30.1% for SS. The branch with close proximity roads had over two‐three times per area SS yield than the branch without such roads. Hysteresis loops showed typical clockwise patterns for the September storm and more complicated patterns for Sandy, reflecting the multipeak event. Estimates of SS and hysteresis in minimally disturbed watersheds provide useful information that can be compared spatially and temporally to facilitate management.     

Green and Ampt infiltration model extended beyond rain duration

A simple method requiring only hand calculations is presented in this study that enables the use of the Green and Ampt infiltration model beyond the rain duration. The method takes into account that the runoff and infiltration processes continue for some period of time after the rain stops. Both the ground surface and subsurface characteristics are considered. A conjunctive overland flow‐infiltration mathematical model is employed for this purpose. A kinematic‐wave approach is used to model the overland flow, and the Green and Ampt equations are employed to calculate the infiltration rates. The governing equations are expressed and solved in terms of dimensionless parameters to enable the generalization of the results based on the principle of hydrologic similarity. A four‐point finite difference scheme is used to solve the governing equations. The results are presented in chart form. An example application of the proposed method is included.     

Surface runoff estimation over heterogeneous foothills of Aravalli mountain using medium resolution remote sensing rainfall data with soil conservation system‐curve number method: A case of semi‐arid ungauged Manesar Nala watershed

Manesar Nala watershed, having an aerial extent of 71.53 km², was subjected to modelling of its hydrological behaviour for assessing its water resource potential. Modern tools and techniques of Remote Sensing (RS) and Geographic Information System (GIS) were used for assessment of runoff generating potential using the Hydrologic Soil Cover Complex (HSCC) Method [U.S. Department of Agriculture (USDA)‐Soil Conservation System‐Curve Number (SCS‐CN) approach]. RS and GIS were used in generation and integration of thematic maps [such as Land use/Land cover (using LISS‐III data) and Hydrologic Soil Group (HSG), (using soil map of study area) to derive the Curve Number (CN) for simulating Runoff (R_o)]. The daily rainfall (P) data for the study period 2002–2015 were acquired from NOAA Climate Prediction Center (NCPC). Corresponding R_o from the watershed for intense storm events for 14 years were calculated through RS and GIS. GIS and SCS‐CN model was employed for modelling the runoff production to study its hydrological behaviour. The study showed that the Manesar Nala watershed was having a composite Curve Number – II (CN_II) value of 82.5 for normal conditions. For dry and wet conditions these values were estimated at 66.44 (CN_I) and 91.56 (CN_III), respectively. This investigation showed that Manesar Nala watershed exhibited an annual average (of 14 years, 2002–2015) R_o volume of 4 542 514.37 m³ based on the average annual rainfall (P) of 0.72 m (720 mm). The average annual surface runoff (R_o) was predicted to be approximately 0.21 m with annual runoff coefficient (C_R) of 0.29. During the study, we also found a strong correlation ‘r’ between satellite driven P and R_o from NRCS‐CN method of the order of 0.94. The methodology so developed has the potential to be used in other similar ungauged watersheds in the same agro‐climatic conditions for the purpose of planning of watershed conservation measures and other developmental activities.     

开封市区地热水可开采量评价

评价地热水可采量时，评价方法的选用对于评价的结果有着重要的意义。根据开封市区地下热流系统的特征和已有的地热资料，可采量的评价方法可选用侧向迳流补给法和均匀布井法(改进的均匀布井法)这两种方法。通过这两种方法分别对开封市区300～1600m热储层的可采热水量进行了评价，分析得出改进的均匀布井法计算结果更为合理。故以改进的均匀布井法计算的可采水量作为开封市区的允许开采量。     

基于GIS的LL-Ⅱ分布式降雨径流模型的结构

主要讨论了LILAN—Ⅱ分布水文模型的结构。该模型结构是为水文过程模拟和预报而设计的，它提出了变动生态产流模式，耦舍了一维坡面流、一维壤中流、一维地下水流、一维河川径流和二维土壤含水量方程组。通过实际检验，该模型能够明显改善模拟预报精度、增强数值计算稳定性、提高参数优选的运行速度和减少存储空间，能够适合不同水文特征地区的产汇流计算，可以提供流域内任意空间网格的水文计算过程。