Straw mulching alters the composition and loss of dissolved organic matter in farmland surface runoff by inhibiting the fragmentation of soil small macroaggregates

Straw mulching is a widespread practice for reducing the soil carbon loss caused by erosion.However,the effects of straw mulching on dissolved organic matter(DOM)runoff loss from black soil are not well studied.How straw mulching affects the composition and loss of runoff DOM by changing soil aggregates remains largely unclear.Here,a straw mulching treatment was compared to a no mulching treatment(as a control)on sloping farmland with black soil erosion in Northeast China.We divided the soil into large macroaggregates(>2 mm),small macroaggregates(0.25-2 mm),and microaggregates(<0.25 mm).After five rain events,the effects of straw mulching on the concentration(characterized by dissolved organic carbon(DoC)and composition(analyzed by fluorescence spectroscopy)of runoff and soil aggregate DOM were studied.The results showed that straw mulching reduced the runoff amount by 54.7%.Therefore,although straw mulching increased the average DOc concentration in runoff,it reduced the total runoff DOM loss by 48.3%.The composition of runoff DOM is similar to that of soil,as both contain humic-like acid and protein-like components.With straw mulching treatment,the protein-like components in small macroaggregates accumulated and the protein-like components in runoff declined with rain events.Fluorescence spectroscopy technology may help in understanding the hydrological paths of rain events by capturing the dynamic changes of runoff and soil DOM characteristics.A variation partitioning analysis(VPA)indicated that the DOM concentration and composition of microaggregates explained 68.2%of the change in runoff DOM from no mulching plots,while the change in runoff DOM from straw mulching plots was dominated by small macroaggregates at a rate of 55.1%.Taken together,our results demonstrated that straw mulching reduces the fragmentation of small macroaggregates and the loss of microaggregates,thus effecting DOM compositions in soil and reducing the DOM loss in runoff.These results provide a theoretical basis for reducing carbon loss in sloping farmland.

Assessment of runoff changes in the sub-basin of the upper reaches of the Yangtze River basin, China based on multiple methods

Quantitative assessment of the impact of climate variability and human activities on runoff plays a pivotal role in water resource management and maintaining ecosystem integrity.This study considered six sub-basins in the upper reaches of the Yangtze River basin,China,to reveal the trend of the runoff evolution and clarify the driving factors of the changes during 1956–2020.Linear regression,Mann-Kendall test,and sliding t-test were used to study the trend of the hydrometeorological elements,while cumulative distance level and ordered clustering methods were applied to identify mutation points.The contributions of climate change and human disturbance to runoff changes were quantitatively assessed using three methods,i.e.,the rainfall-runoff relationship method,slope variation method,and variable infiltration capacity(Budyko)hypothesis method.Then,the availability and stability of the three methods were compared.The results showed that the runoff in the upper reaches of the Yangtze River basin exhibited a decreasing trend from 1956 to 2020,with an abrupt change in 1985.For attribution analysis,the runoff series could be divided into two phases,i.e.,1961–1985(baseline period)and 1986–2020(changing period);and it was found that the rainfall-runoff relationship method with precipitation as the representative of climate factors had limited usability compared with the other two methods,while the slope variation and Budyko hypothesis methods had highly consistent results.Different factors showed different effects in the sub-basins of the upper reaches of the Yangtze River basin.Moreover,human disturbance was the main factor that contributed to the runoff changes,accounting for 53.0%–82.0%;and the contribution of climate factors to the runoff change was 17.0%–47.0%,making it the secondary factor,in which precipitation was the most representative climate factor.These results provide insights into how climate and anthropogenic changes synergistically influence the runoff of the upper reaches of the Yangtze River basin.

Responses of runoff to changes in climate and human activities in the Liuhe River Basin, China

Since the 1950s,numerous soil and water conservation measures have been implemented to control severe soil erosion in the Liuhe River Basin(LRB),China.While these measures have protected the upstream soil and water ecological environment,they have led to a sharp reduction in the downstream flow and the deterioration of the river ecological environment.Therefore,it is important to evaluate the impact of soil and water conservation measures on hydrological processes to assess long-term runoff changes.Using the Soil and Water Assessment Tool(SWAT)models and sensitivity analyses based on the Budyko hypothesis,this study quantitatively evaluated the effects of climate change,direct water withdrawal,and soil and water conservation measures on runoff in the LRB during different periods,including different responses to runoff discharge,hydrological regime,and flood processes.The runoff series were divided into a baseline period(1956-1969)and two altered periods,i.e.,period 1(1970-1999)and period 2(2000-2020).Human activities were the main cause of the decrease in runoff during the altered periods,contributing 86.03%(-29.61 mm),while the contribution of climate change was only 13.70%(-4.70 mm).The impact of climate change manifests as a decrease in flood volume caused by a reduction in precipitation during the flood season.Analysis of two flood cases indicated a 66.00%-84.00%reduction in basin runoff capacity due to soil and water conservation measures in the upstream area.Soil and water conservation measures reduced the peak flow and total flood volume in the upstream runoff area by 77.98%and 55.16%,respectively,even with nearly double the precipitation.The runoff coefficient in the reservoir area without soil and water conservation measures was 4.0 times that in the conservation area.These results contribute to the re-evaluation of soil and water conservation hydrological effects and provide important guidance for water resource planning and water conservation policy formulation in the LRB.

Runoff change in the Yellow River Basin of China from 1960 to 2020 and its driving factors

Analysing runoff changes and how these are affected by climate change and human activities is deemed crucial to elucidate the ecological and hydrological response mechanisms of rivers.The Indicators of Hydrologic Alteration and the Range of Variability Approach(IHA-RVA)method,as well as the ecological indicator method,were employed to quantitatively assess the degree of hydrologic change and ecological response processes in the Yellow River Basin from 1960 to 2020.Using Budyko's water heat coupling balance theory,the relative contributions of various driving factors(such as precipitation,potential evapotranspiration,and underlying surface)to runoff changes in the Yellow River Basin were quantitatively evaluated.The results show that the annual average runoff and precipitation in the Yellow River Basin had a downwards trend,whereas the potential evapotranspiration exhibited an upwards trend from 1960 to 2020.In approximately 1985,it was reported that the hydrological regime of the main stream underwent an abrupt change.The degree of hydrological change was observed to gradually increase from upstream to downstream,with a range of 34.00%-54.00%,all of which are moderate changes.However,significant differences have been noted among different ecological indicators,with a fluctuation index of 90.00%at the outlet of downstream hydrological stations,reaching a high level of change.After the mutation,the biodiversity index of flow in the middle and lower reaches of the Yellow River was generally lower than that in the base period.The research results also indicate that the driving factor for runoff changes in the upper reach of the Yellow River Basin is mainly precipitation,with a contribution rate of 39.31%-54.70%.Moreover,the driving factor for runoff changes in the middle and lower reaches is mainly human activities,having a contribution rate of 63.70%-84.37%.These results can serve as a basis to strengthen the protection and restoration efforts in the Yellow River Basin and further promote the rational development and use of water resources in the Yellow River.

Glacier area change and its impact on runoff in the Manas River Basin,Northwest China from 2000 to 2020

Understanding the distribution and dynamics of glaciers is of great significance to the management and allocation of regional water resources and socio-economic development in arid regions of Northwest China.In this study,based on 36 Landsat images,we extracted the glacier boundaries in the Manas River Basin,Northwest China from 2000 to 2020 using eCognition combined with band operation,GIS(geographic information system)spatial overlay techniques,and manual visual interpretation.We further analyzed the distribution and variation characteristics of glacier area,and simulated glacial runoff using a distributed degree-day model to explore the regulation of runoff recharge.The results showed that glacier area in the Manas River Basin as a whole showed a downward trend over the past 21 a,with a decrease of 10.86%and an average change rate of–0.54%/a.With the increase in glacier scale,the number of smaller glaciers decreased exponentially,and the number and area of larger glaciers were relatively stable.Glacier area showed a normal distribution trend of increasing first and then decreasing with elevation.About 97.92%of glaciers were distributed at 3700–4800 m,and 48.11%of glaciers were observed on the northern and northeastern slopes.The retreat rate of glaciers was the fastest(68.82%)at elevations below 3800 m.There was a clear rise in elevation at the end of glaciers.Glaciers at different slope directions showed a rapid melting trend from the western slope to the southern slope then to the northern slope.Glacial runoff in the basin showed a fluctuating upward trend in the past 21 a,with an increase rate of 0.03×10^(8) m^(3)/a.The average annual glacial runoff was 4.80×10^(8) m^(3),of which 33.31%was distributed in the ablation season(June–September).The average annual contribution rate of glacial meltwater to river runoff was 35.40%,and glacial runoff accounted for 45.37%of the total runoff during the ablation season.In addition,precipitation and glacial runoff had complementary regulation patterns for river runoff.The findings can provide a scientific basis for water resource management in the Manas River Basin and other similar arid inland river basins.

The changes in the annual distribution of mountain runoff during the period of 1965-2018 in Hexi Corridor,Northwest China

The annual distribution characteristics of river runoff in arid regions have significant implications for water resource stability and management.Based on the mountain runoff data from 1965 to 2018,this study examines the annual change characteristics of monthly runoff of the Shiyang River Basin,Heihe River Basin,and Shule River Basin in the Hexi Corridor,Northwest China.Many indexes are used and analyzed,including the coefficient of variance,the complete regulation coefficient,the concentration degree and concentration period,the magnitude of change,the skewness coefficient,and the kurtosis coefficient of the annual distribution curves.The results reveal the following:(1)The inhomogeneity of annual runoff distribution in the Taolai River and the rivers to the west of it,except the Shiyou River,show an increasing trend.Conversely,the inhomogeneity of the rivers to the east of the Taolai River generally show a downward trend,but the coefficient of variance value is still very high.(2)In the Shiyang River Basin,the annual distribution of the concentration period is characterized by a relatively discrete pattern.Conversely,the Heihe River Basin exhibits a relatively concentrated pattern,and the distribution pattern of the Shule River Basin is quite different.Notably,all concentration periods in the three basins have shifted backward after the 2000s.(3)The Shiyang River Basin exhibits disordered annual distribution curves of runoff in different years.In contrast,the Heihe River Basin presents a typical‘single-peak’pattern with a prominent right-skewed.The Shule River Basin has regular distribution curves,with a gradually significant‘double-peak’pattern from east to west.Overall,there has been a slight change in runoff in the Shiyang River Basin,while the Heihe River Basin and Shule River Basin have experienced significant increases in runoff.The annual distribution curves of runoff in the Liyuan River and the rivers to the east of it exhibit a gentle peak pattern,and the appearance probability of extreme runoff during the year is low.Conversely,the rivers to the west of the Liyuan River,excluding the Danghe River,display a sharp peak and thick tail pattern,indicating that the appearance probability of extreme runoff during the year is high.These findings have practical implications for the planning and management of water resources in the Hexi Corridor.Moreover,they provide a solid foundation for predicting future changes in regional water resources.

Comparative Assessment of Impacts of Future Climate Change on Runoff in Upper Daqinghe Basin,China

Assessing runoff changes is of great importance especially its responses to the projected future climate change on local scale basins because such analyses are generally done on global and regional scales which may lead to generalized conclusions rather than specific ones.Climate change affected the runoff variation in the past in the upper Daqinghe Basin,however,the climate was mainly considered uncertain and still needs further studies,especially its future impacts on runoff for better water resources management and planning.Integrated with a set of climate simulations,a daily conceptual hydrological model(MIKE11-NAM)was applied to assess the impact of climate change on runoff conditions in the Daomaguan,Fuping and Zijingguan basins in the upper Daqinghe Basin.Historical hydrological data(2008–2017)were used to evaluate the applicability of the MIKE11-NAM model.After bias correction,future projected climate change and its impacts on runoff(2025–2054)were analysed and compared to the baseline period(1985–2014)under three shared social economic pathways(SSP1-2.6,SSP2-4.5,and SSP5-8.5)scenarios from Coupled Model Intercomparison Project Phase 6(CMIP6)simulations.The MIKE-11 NAM model was applicable in all three Basins,with both R^(2)and Nash-Sutcliffe Efficiency coefficients greater than 0.6 at daily scale for both calibration(2009–2011)and validation(2012–2017)periods,respectively.Although uncertainties remain,temperature and precipitation are projected to increase compared to the baseline where higher increases in precipitation and temperature are projected to occur under SSP2-4.5 and SSP5-8.5 scenarios,respectively in all the basins.Precipitation changes will range between 12%–19%whereas temperature change will be 2.0℃–2.5℃ under the SSP2-4.5 and SSP5-8.5 scenarios,respectively.In addition,higher warming is projected to occur in colder months than in warmer months.Overall,the runoff of these three basins is projected to respond to projected climate changes differently because runoff is projected to only increase in the Fuping basin under SSP2-4.5 whereas decreases in both Daomaguan and Zijingguan Basins under all scenarios.This study’s findings could be important when setting mitigation strategies for climate change and water resources management.

Runoff Characteristics of Different Stands in Dongjiang Lake Reservoir Area

Different forest stands in the Dongjiang Lake Reservoir area of Zixing were selected as the research objects to study the characteristics of runoff generation in different forest stands.The results showed that there was no significant difference in annual runoff among M3,M1,and M5,and no significant difference between each forest stand and the control.The order was M3(22.75 mm)>M1(21.77 mm)>M5(20.14 mm).Forest vegetation generates less runoff through vegetation restoration compared to the control,indicating that forest vegetation reconstruction and restoration are beneficial for soil and water conservation.

Response of runoff to climate change in the area of runoff yield in upstream Shiyang River Basin,Northwest China:A case study of the Xiying River

The objective of this study was to analyze the response of runoff in the area of runoff yield of the upstream Shiyang River basin to climate change and to promote sustainable development of regional water resources and ecological environment.As the biggest tributary of the Shiyang River,Xiying River is the only hydrological station(Jiutiaoling) that has provincial natural river and can achieve long time series monitoring data in the basin.The data obtained from this station is representative of natural conditions because it has little human activites.This study built a regression model through identifying the characteristics of runoff and climate change by using Mann-Kendall nonparametric statistical test,cumulative anomaly,and correlation analysis.The results show that the average annual runoff is 320.6 million m3/a with the coefficient of variation of 0.18 and shows slightly decrease during 1956-2020.It has a significant positive correlation the average annual precipitation(P<0.01).Runoff is sensitive to climate change,and the climate has becoming warm and wet and annual runoff has entering wet period from 2003.Compared to the earlier period(1955-2000),the increases of average annual temperature,precipitation and runoff in recent two decades were 15%,9.3%,and 7.8%,respectively.Runoff in the Shiyang River is affected by temperature and precipitation among climate factors,and the simulation results of the runoff-climate response model(R=0.0052P-0.1589T+2.373) indicate that higher temperature leads to a weakening of the ecological regulation of surface runoff in the flow-producing area.

Field experiments on quantifying the contributions of Coreopsis canopies and roots to controlling runoff and erosion on steep loess slopes

Grass recovery is often implemented in the loess area of China to control erosion.However,the effect mechanisms of grass cover on runoff erosion dynamics on steep loess hillslopes is still not clear.Taking the typical forage species(Coreopsis)in semiarid areas as subject,this study quantified the effects of canopies and roots on controlling slope runoff and erosion.A series of field experiments were conducted in a loess hilly region of China.Field plots(5 m length,2 m width,25°slope gradient)constructed with three ground covers(bare soil;Coreopsis with intact grass;only roots of Coreopsis),were applied with simultaneous simulated rainfall(60mm h^(-1))and upslope inflow(10,30,50,70,90L min^(-1)).The results showed that compared with bare soil,intact grass significantly reduced runoff and soil loss rates by 16.6% and 62.4% on average,and decreased soil erodibility parameter by 66.3%.As inflow rate increased,the reductions in runoff and soil loss rates increased from 2.93 to 14.00 L min^(-1)and 35.11 to 121.96 g m^(-2)min^(-1),respectively.Canopies relatively contributed 66.7% to lowering flow velocity,turbulence,weakening erosive force and increasing hydraulic resistance.Roots played a predominant role in reducing soil loss and enhancing soil antierodibility,with relative contributions of 78.8% and 73.8%.Furthermore,the maximum erosion depth reduced by Coreopsis was at the upper slope section which was previously eroded the most.These results demonstrated the efficiency of Coreopsis cover in controlling runoff and erosion on steep loess slopes,especially under large inflow rates and at upper slope sections.We suggest protecting Coreopsis with intact grass at upper slope sections,while the aboveground grass biomass can be used for grazing or harvesting at middle and lower slope sections,with roots reserved.

基于数值试验的降雨径流过程对不透水面空间分布的响应分析

为解析降雨径流过程对不透水面空间分布的响应关系,构造了一个3 km×3 km的假想试验区域,面向试验区域构建了包含6个不透水率的36种不透水面空间分布,并建立相应的数值试验模型,模拟了重现期分别为2、5、10、20、50、100 a共6种不同重现期短历时设计降雨下的降雨径流过程,基于模拟结果对不同不透水面空间分布情景下的降雨径流过程进行了分析。结果表明:在同一不透水率下,不同不透水面空间分布的径流系数差异相对较小,不透水面空间分布对径流特征的影响主要体现在径流峰值和峰现时间上;在同一降雨条件下,不透水率变化是径流过程变化的主导因素,径流系数与不透水率呈线性相关关系,随着不透水率的增加,径流过程线逐渐由“矮胖”变得“尖瘦”。

Influence of water conservancy project on runoff in the source region of the Yellow River and wetland changes in the Lakeside Zone,China

The source area of the Yellow River(SAYR),located above the Huangheyan hydrological station,is important for ecological preservation and water source conservation in the Yellow River Basin.In this area,the impact of water conservation projects on the hydrology and the ecological environment is pivotal in protecting water resources and alpine vegetation ecosystems.This study investigates the impact of the Yellow River Source Hydropower Station on the runoff and ecological evolution of the SAYR,along with the underlying mechanism,using extensive datasets encompassing long-term meteorological,hydrological and remote sensing data from various time periods.Results show that,over the long term,precipitation is the primary factor driving runoff variations in the SAYR.Nevertheless,from 1990 to 2020,there is a notably inconsistent relationship between precipitation and runoff.After the completion of the Yellow River Source Hydropower Station in 2001,the water level of Eling Lake experienced and elevation of 2–3 m,leading to a gradual recovery of runoff.In addition,the basin's water balance shifted from a negative to a positive equilibrium,oscillating with changes in lake water levels.Consequently,the overflow zone of the Tangchama alluvial–proluvial fan in the upper reaches of the lakeshore shifted by 500 m,and marsh wetlands expanded by 20.78 km^(2).The increased storage of lakes and groundwater in the SAYR is the key controlling factor for the runoff recovery,changes in the basin's water balance,and enhancements in lakeshore vegetation ecology.Under the geological background of the Qinghai–Tibet Plateau's upliftment and intensified upstream river erosion,the basin experienced a substantial water imbalance due to declining discharge base levels,which is the most critical factor behind runoff attenuation in the SAYR towards the end of the 20th century.The construction of the hydropower station objectively raised the drainage base level of the basin,thereby positively contributing to the preservation of water balance,runoff stability,and the enhancement of swamps and wetlands along the lakeshore.

尾巨桉萌芽林与混交改造林径流水质变化特征

【目的】探讨桉树纯林及桉树混交林坡面径流水质变化特征,揭示水质变化的客观规律,为正确回答和解决桉树人工林水质问题,实现桉树人工林可持续发展提供重要科学依据。【方法】以桉树纯林、桉树×灰木莲混交林(带状混交、行间混交、株间混交)、灰木莲纯林为研究对象,选取对森林水质有关键影响作用的因子,采用连续监测与实验室分析相结合的方法,对比不同栽培模式条件下径流水质变化差异。【结果】1)试验样地坡面径流水pH值、COD、BOD5均达到我国农田灌溉水质标准(GB 5084—2021)对pH值(5.5~8.5)、COD(<150.00 mg·L^(-1))、BOD5(<60.00 mg·L^(-1))浓度的要求;2)桉树纯林坡面径流水中单宁含量(7.77 mg·L^(-1))显著高于其他样地,达到空白对照样地(1.22 mg·L^(-1))的6.4倍,桉树×灰木莲混交后可以有效降低坡面径流水中单宁含量,其中桉树×灰木莲行间混交模式效果最明显;3)桉树和灰木莲纯林坡面径流水中腐殖酸含量均高于混交林,其中桉树×灰木莲带状混交模式更有利于其坡面径流水中腐殖酸含量的降低。【结论】桉树混交模式的营建在保证坡面径流水质主要指标达标的同时能有效降低坡面径流水中单宁及腐殖酸含量,桉树混交栽培模式进一步缓解了桉树纯林对土壤酸碱性及微生物的影响。

疏勒河流域径流量和输沙量变化规律

[目的]探索疏勒河流域水沙变化特性,可为国家实施西部生态安全战略提供科学支撑。[方法]基于疏勒河流域昌马堡、潘家庄、党城湾3个水文站的实测径流量和输沙量序列资料,运用滑动平均、Mann-Kendall突变趋势检验和小波分析法等方法,分析了疏勒河流域径流量和输沙量变化规律。[结果]疏勒河流域年径流量和年输沙量均呈递增趋势,且输沙量增大趋势大于径流量,昌马堡、潘家庄、党城湾3个水文站径流量分别在1999年、2016年、1982年发生突变,昌马堡和潘家庄年输沙量突变均发生在1998年,党城湾输沙量没有突变;疏勒河流域3个代表站的径流量和输沙量都呈现出多时间尺度的演化特征,昌马堡径流量主周期为58 a,31 a,14 a,9 a和5 a,输沙量主周期为48 a,23 a,14 a,7 a和5 a,潘家庄径流量主周期为59 a,32 a,14 a,输沙量主周期为37 a,14 a,8 a和5 a,党城湾径流量主周期为42 a和5 a,输沙量主周期为16 a和8 a。[结论]疏勒河流域水沙总体呈递增趋势,且存在明显的周期变化,除党城湾的输沙量没有突变发生以外,其余站点水沙均有突变发生,同一水文站输沙量的突变的发生滞后于径流量的突变。

不同配置乡村植被缓冲带阻控径流污染特征研究

植被缓冲带是河湖的重要生态空间屏障,对于减缓人类活动对河湖的直接干扰、阻隔农业面源污染等具有重要意义。为系统研究不同类型缓冲带对农田氮磷等污染物的拦截功效,本研究在定远张山设计8个缓冲带小区,结合自然降雨方式,持续两年观测不同缓冲带对地表径流及其主要污染物(TN、TP、COD)的削减效果。结果表明:林地和3°、8°横垄耕地缓冲带对径流的拦截效率较高,减流率分别达到了62.4%、52.0%和60.6%,径流量随雨强增大先升高后下降。与8°坡耕地缓冲带相比,降坡(3°)处理竖垄、横垄缓冲带泥沙流失量分别降低53.3%、50.9%。降雨产流的养分流失以氮素和有机质为主,林地缓冲带对径流NH4+-N的拦截率平均高达95.2%,此外降坡和横垄耕作措施也能有效减少径流冲刷的氮素流失。不同处理缓冲带对径流TP均有较好的拦蓄效果。3°、8°横垄耕地缓冲带CODMn流失量较低,拦截率达到53.0%、58.6%。林地缓冲带中高覆盖度的植被和发达的根系能够有效减缓降雨对地表的冲刷,减少径流和养分流失。在南方丘陵山地的乡村地区实施横坡垄作是拦蓄径流、降低面源污染风险的有效措施。

Methodology for the Calculation of the Runoff Coefficient with the Arrangement Tirado

For this research work, an adequate methodology was sought for the calculation of the runoff coefficient with the Tirado arrangement. To achieve this, first, the variables that affect the runoff coefficient were identified, then the model was described with the Tirado arrangement, and as a third part for the calculation of the runoff coefficient, the Tirado model is proposed. From the theory for the calculation of the runoff coefficient, the equation of the weighted coefficients and the expression of Nadal were manipulated, resulting in the following relationship , considering this as the expression for the arrangement Tirado. The expression is tested with different intensities, the magnitudes correspond to 150, 200, 250 and 300 mm/hrs, resulting in runoff coefficient 0.82, 0.87, 0.89, 0.91 respectively. This means that, the higher the intensity, the runoff coefficient will be higher, logically the characteristics of the basin affect that this coefficient has variation in the space studied.

Runoff-Water Properties from Various Soils as Affected by Struvite-Phosphorus Source and Water Type

Struvite (MgNH4PO4?6H2O) can be produced from municipal wastewater and has been shown to be an alternative fertilizer-phosphorus (P) source for various crops, but little is known about the runoff-water-quality implications from soil-applied struvite. The objective of this study was to evaluate the effects of soil [Creldon (Oxyaquic Fragiudalfs), Dapue (Fluventic Hapludolls), Roxana (Typic Udifluvents), and Calloway (Aquic Fraglossudalfs) series], fertilizer-P source [synthetically produced electrochemically precipitated struvite (ECSTsyn), real-wastewater-derived ECST (ECSTreal), chemically precipitated struvite (CPST), and monoammonium phosphate (MAP)], and water source (rainwater, groundwater, and struvite-removed real wastewater) over time on runoff-water-quality parameters from laboratory-conducted, rainfall-runoff simulations. Mesh tea bags containing each soil-fertilizer treatment combination were rained on with each water source (Trial 1), incubated for 6 months, and rained on again (Trial 2) to evaluate runoff-water quality. Struvite fertilizers had similar runoff-water-quality properties to those from MAP. In Trial 1, runoff total P (TP) concentration differences (i.e., soil-fertilizer-water-type response minus control response minus blank response) from ECSTsyn or ECSTreal were 1 to 5 times larger than MAP and CPST for all water-soil-fertilizer-P source treatment combinations, except for the Creldon-groundwater and Roxana-wastewater combinations. In both trials, runoff TP decreased over time in all water-soil and soil-fertilizer-P source treatment combinations, except for the Roxana-CPST combination where TP increased over time by 46%. The similar water-quality responses from the struvite fertilizers among the various soils and water types compared to MAP suggest that struvite has similar runoff-water-quality implications as at least one widely used, commercially available fertilizer-P source.

基于径流事件的农业面源监测采样间隔分析

选择丹江口库区的五龙池小流域为对象,以典型降雨径流事件的水质水量加密监测数据作为径流过程真实值,通过不同时间间隔和水量间隔模拟采样,分析污染负荷通量估算误差,并确定有效采样间隔.结果显示,五龙池小流域降雨径流事件具有明显的峰值特征(初始流量55m^(3)/h,峰值流量977.3m^(3)/h),TP浓度与径流高度同步(初始浓度为0.05mg/L,峰值浓度为0.25mg/L),TN随径流达到峰值后下降不明显(初始浓度为2mg/L,峰值浓度为8mg/L).模拟采样表明,时间间隔5,10,15,20,30,60,120,240,480,720min,采样点数量从1957个减少到14个;水量间隔16,32,64,128,256,384,576,800,1600,3200m^(3),采样点数量从2893个减少到14个;水量间隔采样对径流峰值的捕捉能力明显高于时间间隔采样.负荷估算误差显示,TP误差波动大于TN;以±5%作为允许的误差范围,降雨径流事件采样监测的有效时间间隔为120min,有效水量间隔为1600m^(3).

SCS-CN and GIS-Based Approach for Estimating Runoff in Western Region of Saudi Arabia

Designing reservoir operations, hydraulic structure, and soil erosion management techniques all require an estimation of a potential runoff. Accurate runoff in-formation is typically scarce in Saudi Arabia—a significant challenge for hydrologists. Wadi-Rahjan catchment in Western Saudi Arabia has been taken as a case study to determine the potential runoff estimates. The study integrates the soil conservation service curve number (SCN-CN) technique, remote sensing (RS), and geographical information system (GIS). Critical parameters including the digital elevation model (DEM), land use/land cover (LULC), hydrologic soil groups (HSGs), and rainfall data were also employed. The curve number (CN), which shows the catchment’s reaction to a storm was estimated based on LULC and HSG layers. The CN map obtained and rainfall data were employed in the GIS-based SCS-CN model to develop the potential runoff map. Based on the results of calculations, the study area is classified into three HSGs, namely, B, C, D. Averagely, CN for a normal condition is 90 while wet and dry conditions are 97 and 80, respectively. Results obtained from the SCS-CN method’s calculations reveal a yearly runoff result that varies from 194 mm to 295 mm. A higher percentage of runoff water (35%) in a runoff range from 289 to 295 mm, followed by 24%, ranged 269 to 288 mm. An interesting rainfall-runoff regression evaluation reveals a good 0.90 correlation. Other watersheds in Saudi Arabia may use this method for planning and development.

An Evaluation of Manure Management Strategies, Phosphorus Surface Runoff Potential and Water Usage at an Arkansas Discovery Dairy Farm

Manure management is an essential component of dairy production. Nutrient-laden, field-applied dairy manure often serves as a fertilizer source, but can also pose environmental threats if not properly managed. The Haak dairy farm, located in Decatur, Arkansas, was granted a permit by the Arkansas Department of Environmental Quality (ADEQ) to employ a unique method in treating and storing cattle manure generated during the milking process. This method includes minimizing water use in wash water, dry scraping solids to combine with sawdust for composting and pumping effluent underground into a sloped concrete basin that serves as secondary solid separator before transporting the manure effluent into an interception trench and an adjacent grassed field to facilitate manure nutrient uptake and retention. The Arkansas Discovery Farm program (ADF) is conducting research to evaluate the environmental performance of the dairy’s milk center wash water treatment system (MCWW) by statistical analysis, characterization of phosphorus (P) migration in soil downslope from the inception trench, temperature measurements, and nutrient analysis of a stored dry stack manure/sawdust mixture. Goals included determining possible composting effectiveness along with comparisons to untreated dairy manure and quantifying the use of on-farm water. Results from this research demonstrated that: 1) The MCWW was effective at retaining manure-derived nutrients and reducing field nutrient migration as the MCWW interception trench had significantly higher total nitrogen (TN) (804.2 to 4.1), total phosphorus (TP) (135.6 to 1.5), and water extractable phosphorus (WEP) (55.0 to 1.0) concentrations in milligrams per liter (mg⋅L-1) than the downhill freshwater pond respectively;2) temperature readings of the manure dry stack indicated heightened levels of microbial and thermal activity, but did not reach a standard composting temperature of 54°C;3) manure dry stack nutrient content was typically higher than untreated dairy manure when measured on a “dry basis” in ppm, but was lower on an “as is basis” in ppm and kg/metric ton;and 4) water meter readings showed that the greatest use of on-farm water was for farm-wide cattle drinking (18.77), followed by water used in the milking center (3.45) and then followed by human usage (0.02) measured in cubic meters per day (m3⋅d-1). These results demonstrate that practical innovations in agricultural engineering and environmental science, such as the Haak dairy’s manure treatment system, can effectively reduce environmental hazards that accompany the management of manure at this dairy operation.