Environmental Factors, Constraints and Risks of Rainwater Runoff in Commune II of Maradi (Republic of Niger)

The Urban Commune of Maradi in Niger experienced increasingly frequent flooding following rainy episodes generating volumes and water flows that are difficult to control in recent years. This study aims to determine the impacts of runoff water in Commune II of Maradi City and to assess the role of urban planning in runoff management, as well as the strengths and weaknesses of urban sanitation in Maradi. The methodological approach used consisted of: 1) an interpretation of documentary data, 2) gathering information on runoff at several sites in the study area, and 3) interviews and questionnaires with local communities. This approach made it possible to understand the degree of vulnerability of the populations to flooding and then to propose sustainable solutions to reduce the vulnerability of the affected populations, through the implementation of effective urban rainwater management practices (USWMP). The results show that the impacts of runoff are mainly related to the lack of adequate storm water drainage networks in the area, but also to the nature of the habitats. Geomorphological factors such as the nature of the soil, the slope of the terrain and the altitude increase the degree of risk. In addition, the inadequacy and dilapidation of the drainage systems of the canals and above all the anarchic occupation of the land linked to accelerated urbanization are the cause of flooding by stagnation of rainwater. A phenomenon now linked to numerous deteriorations of urban equipment, the runoff of rainwater in the city of Maradi carries so many pollutants that municipalities, businesses and individuals should put in place pollution prevention measures.

Stormwater Runoff Pollution in a Rural Township in the Hilly Area of the Central Sichuan Basin,China

Stormwater runoff in rural townships has a high potential for water quality impairment but little information is available on strormwater runoff pollution from rural townships.To investigate the characteristics of runoff pollution in a rural township,a catchment(2.32 ha) in Linshan Township,Sichuan,China was selected to examine runoff and quality parameters including precipitation,flow rate,and total nitrogen(TN),dissolved nitrogen(DN),total phosphorus(TP),dissolved phosphorus(DP),particulate phosphorus(PP),chemical oxygen demand(COD) and suspended solid(SS) in 12 rainfall events occurring between June 2006 and July 2007.Results show that the annual pollutant loads were 47.17 kg ha-1 for TN,6.64 kg ha-1 for TP,1186 kg ha-1 for COD,and 4297 kg ha-1 for SS.DN and PP were the main forms of nitrogen and phosphorus in stormwater runoff.TP,COD and SS showed medium mass first flushes,in which nearly 40% of the total pollutant masses were transported by the first 30% of total flow volume.The peak of pollutant concentration appeared before the peak of runoff due to the first flush of accumulative pollutants in impervious areas and drainage ditches.The EMC values of TN,TP,DN and PP were negatively correlated to the maximum rainfall intensity,precipitation,total flow volume,and runoff duration(P<0.05,n=12),while EMC of COD and SS were not related to any rainfall characteristics.The FF30(FF,First Flush) for TN,TP,COD and SS were positively correlated to the maximum rainfall intensity(P<0.05,n=12),and TP was also positively correlated to the average rainfall intensity(P<0.05,n=12),indicating that the magnitude of first flush increased with the rainfall intensity in the Linshan Township.

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.

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.

Impact of fertilization on chestnut growth, N and P concentrations in runoff water on degraded slope land in South China

Growing fruit trees on the slopes of rolling hills in South China was causing serious environmental problems because of heavy application of chemical fertilizers and soil erosion. Suitable sources of fertilizers and proper rates of applications were of key importance to both crop yields and environmental protection. In this article, the impact of four fertilizers, i.e., inorganic compound fertilizer, organic compound fertilizer, pig manure compost, and peanut cake （peanut oil pressing residue）, on chestnut （Castanea mollissima Blume） growth on a slope in South China, and on the total N and total P concentrations in runoff waters have been investigated during two years of study, with an orthogonal experimental design. Results show that the organic compound fertilizer and peanut cake promote the heights of young chestnut trees compared to the control. In addition, peanut cake increases single-fruit weights and organic compound fertilizer raises single-seed weights. All the fertilizers increased the concentrations of total N and total P in runoff waters, except for organic compound fertilizer, in the first year experiment. The observed mean concentrations of total N varied from 1.6 mg/L to 3.2 mg/L and P from 0.12 mg/L to 0.22 mg/L, which were increased with the amount of fertilizer applications, with no pattern of direct proportion. On the basis of these experiment results, organic compound fertilizer at 2 kg/tree and peanut cake at 1 kg/tree are recommended to maximize chestnut growth and minimize water pollution.

Discharge Water Quality Models of Storm Runoff in a Catchment

The relationships between the water qualities of nitrogen and phosphorous contents in the discharge water and the discharge of storm runoff of an experimental catchment including terraced paddy field are analyzed based on experiment results of the catchment. By summarizing the currently related research on water quality models, the water quality models of different components of storm runoff of the catchment are presented and verified with the experiment data of water quality analyses and the corresponding discharge of the storm runoffs during 3 storms. Through estimating the specific discharge of storm runoff, the specific load of different components of nitrogen and phosphorus in the discharge water of the catchment can be forecasted by the models. It is found that the mathematical methods of linear regression are very useful for analysis of the relationship between the concentrations of nitrogen and phosphorus and the water discharge of storm runoff. It is also found that the most content of the nitrogen (75%) in the discharge water is organic, while half of the content (49%) of phosphorus in the discharge water is inorganic.

Impacts of water quality variation and rainfall runoff on Jinpen Reservoir,in Northwest China

The seasonal variation characteristics of the water quality of the Jinpen Reservoir and the impacts of rainfall runoff on the reservoir were investigated. Water quality monitoring results indicated that, during the stable stratification period, the maximum concentrations of total ni- trogen, total phosphorus, ammonia nitrogen, total organic carbon, iron ion, and manganese ion in the water at the reservoir bottom on September 6 reached 2.5 mg/L, 0.12 mg/L, 0.58 mg/L, 3.2 mg/L, 0.97 mg/L, and 0.32 rag/L, respectively. Only heavy storm runoff can affect the main reservoir and cause the water quality to seriously deteriorate. During heavy storms, the stratification of the reservoir was destroyed, and the reservoir water quality consequently deteriorated due to the high-turbidity particulate phosphorus and organic matter in runoff. The turbidity and concentrations of total phosphorus and total organic carbon in the main reservoir increased to 265 NTU, 0.224 mg/L, and 3.9 mg/L, respectively. Potential methods of dealing with the water problems in the Jinpen Reservoir are proposed. Both in stratification and in storm periods, the use of measures such as adjusting intake height, storing clean water, and releasing turbid flow can be helpful to safeguarding the quality of water supplied to the water treatment plants.

Runoff Estimation for Suggested Water Harvesting Sites in the Northern Jordanian Badia

Jordan is characterized by severe weather conditions, therefore great temporal and spatial variations in rainfall;runoff and evaporation amounts are expected. Water harvesting has been practiced in Jordan throughout history for both irrigation and household purposes. A major research project was carried out in the Jordanian Badia on site selection criteria for rain water harvesting systems based on the integration between indigenous knowledge and the use of Geo-informatics. This work was followed by conducting a geophysical and soil investigation for five potential sites. In this study, GIS was used to investigate the potential of having enough runoff in the five selected sites to establish water harvesting dams based on rainfall, evaporation data and catchments’ areas for the selected sites. It was found that the estimated runoff that could be harvested on annual basis at these sites varies between 0.2 Million Cubic Meters (MCM) in Alaasra site to 0.82 MCM in Al-Manareh (Al-Ghuliasi) site. This indicates that these sites have the potential for small scale water harvesting that could be utilized by local livestock owners in the area to water their livestock.

Relationship Between Watershed Landscape Pattern Change and Runoff-Sediment in Wind-Water Erosion Crisscross Region

This paper selected the typical wind-water erosion crisscross region Xiliugou watershed for research to reveal the impact of the landscape pattern change of the underlying surface in wind-water erosion crisscross region where soil erosion is most serious on rainfall and runoff as well as erosion and sediment.Based on the Landsat TM image data and measured data of runoff-sediment in that watershed,the paper analyzed the characteristics of watershed landscape pattern change and runoff-sediment and explored the relationship between landscape index and runoff-sediment yield by means of GIS and Fragstats.The results were included as follows.(1)Grassland was the dominant landscape.In terms of the number of patches and area change rate,from 1985 to 2010,cultivated land,forest land and construction land were most stable,followed by unused land.Unused land,grassland and cultivated land experienced the most dramatic conversion and maximally affected by human activities.(2)The inter-annual difference between annual runoff and annual sediment load was significant.Compared with the annual sediment load,the trend of decreasing runoff was more obvious.The correlation coefficient of runoff-sediment was 0.67,representing a significant correlation.(3)There was a significant correlation between the landscape index and runoff-sediment.The runoff was negatively correlated with the largest patch index,patch cohesion index,aggregation index and contagion index,but positively correlated with landscape morphology index and landscape division index.And the sediment was negatively correlated with the contagion index,aggregation index and plaque cohesion index,but positively correlated with other landscape indexes.The results indicate that with the increase of the largest patch index,patch cohesion index and aggregation index,the rainfall infiltration capacity increase obviously and the soil erosion reduce significantly.Therefore,increasing the largest patch index,patch cohesion and aggregation index of the watershed landscape can enhance the function of water storage and soil conservation as well as ecological optimization in the windwater erosion crisscross region.The results can provide theoretical support for the ecological environment construction and comprehensive utilization of water and soil resources.

Effects of Turfgrass Thatch on Water Infiltration, Surface Runoff, and Evaporation

The development of a (layer of) thatch in turfgrass causes important changes to near-surface eco-hydrological processes. In this study, we investigated the effects of turfgrass thatch, specifically Kentucky bluegrass (Poa pratensis L.) and red fescue (Festuca rubra L.) on water infiltration, surface runoff, and soil moisture evaporation. The thatches were collected from the field for controlled experiments using packed soil columns under various rainfall conditions. Results indicated that the presence of thatch delayed the onset of infiltration compared with situations without a thatch at the soil surface. Infiltration was delayed for a longer period in thicker red fescue thatch than thinner Kentucky bluegrass thatch. The presence of a thatch reduced runoff by holding more water locally during the rainfall period and allowing a longer period of time for infiltration. Additionally, evaporative water loss was reduced with the presence of thatch than that of bare soil. Our results highlight that the presence of thatch changes the near-surface hydrological processes, which may help improve turf management practices in terms of thatch control and irrigation scheduling.

Assessment of the Effects of Poultry Litter on Surface Runoff Water Quality from Agricultural Lands

The use of pelletized poultry litter (PPL) as a substitute for inorganic fertilizers is increasingly being en-couraged in states like Delaware which have a considerable surplus of poultry litter. However, we know very little about the impacts of PPL on runoff water quality and whether it is an environmentally-sound and sus-tainable alternative to inorganic fertilizer. To address these questions we compared the exports of nutrients (NH4-N, NO3-N and PO4-P) and trace elements (As, Cu, and Zn) in surface runoff from agricultural plots receiving PPL, raw poultry litter (RPL), urea and no-fertilizer (control) treatments. The study was conducted on agricultural land located in Middletown, Delaware with corn as the cover crop. The experimental plots were 5 m wide and 12 m long with reduced tillage and no-tillage management practices. Sampling was con-ducted for six natural rainfall events from April through August 2008. Nutrient (NH4-N, NO3-N and PO4-P) exports from plots receiving PPL were less than those with urea or raw litter applications. While exports of trace elements from the PPL treatment exceeded those from urea, they were much lower than the corre-sponding exports from the RPL treatments. Mass exports of nutrients and trace elements were correlated with event size (rainfall amount) but were not correlated with timing of event (days since litter application). Results from this study suggest that the use of PPL in combination with no-tillage may provide an environ-mentally safe alternative to synthetic fertilizers.

Analysis on Regulation Effect of Water Conservancy Project in Upper Reaches of Wujiang River,Guizhou on Runoff

Based on monthly runoff data of Hongjiadu,Guizhou from October 2013 to June 2015 and monthly runoff data of Yachi River,Guizhou from April 2014 to May 2015,using REOF and multiple linear regression analysis,regulation effect of water conservancy project in upper reaches of Wujiang River on monthly runoff of the river was analyzed. Seasonal temporal-spatial change of monthly runoff in Hongjiadu and Yachi River mainly contained two kinds of modalities. The first modality was that of Yachi River,which was main component of seasonal change of monthly runoff,and peak appeared in July. Space load of Yachi River modality was larger than Hongjiadu,and manual control ability of monthly runoff in Hongjiadu was larger than Yachi River. The second modality was that of Hongjiadu,and peak appeared in December. Space load of Hongjiadu modality was larger than Yachi River,and manual control ability of monthly runoff in Yachi River was larger than Hongjiadu. Seasonal changes of time components of two modalities had significant inverse phase. Regulation effect of Hongjiadu modality advanced Yachi River modality,and regulation effect of water conservancy project in Hongjiadu modality was larger than that of Yachi River modality,and seasonal distribution characteristics of regional rainfall was basically eliminated in Hongjiadu modality. Some seasonal distribution characteristics of regional rainfall were maintained in Yachi River modality. Monthly runoff modality of Yachi River had water storage regulation effect on a smaller part of regional monthly rainfall modality. Monthly runoff modality of Hongjiadu mainly had water storage regulation effect on south-north type of component of regional monthly rainfall,while most components of regional monthly rainfall modality did not have significant impact on monthly runoff modality of Hongjiadu.

Surface runoff processes and sustainable utilization of water resources in Manas River Basin, Xinjiang, China

Water is the important resource to guarantee the existence and development of oases in arid areas. To improve the utilization efficiency of water resources in Manas River Basin, this paper investigated the trends and periods of runoff based on the runoff and climate data for the past 50 years. Subsequently, with the socioeconomic and water resources data, we studied a comprehensive evaluation on the water security in this area. The results indicated that the stream flows in the three hydrological stations of Hongshanzui, Kensiwat and Bajiahu have sig- nificantly increased and undergone abrupt changes, with periods of 18 and 20 years. According to assessment, water security in the Manas River Basin was at an unsafe level in 2008. In criterion layer, the ecological security index and the index of supply-demand situation are both at the relatively secure level; the quantity index and so- cioeconomic index of water resources are at the unsafe level and basic security level, respectively. Therefore, in order to achieve sustainable economic and social development within the Manas River Basin, it is vital to take a series of effective measures to improve the status of water security.

Hydrological Processes in a Small Research Watershed under Forest Coverage in the Coast of Chiapas, Mexico

In the hydrological watershed, some natural processes take place in which the interaction of water, soil, climate and vegetation favors the capture of water. The present study aimed to evaluate preliminary information regarding the hydrological response and the water balance in a small research watershed with tropical forest cover (15°01'44''N and 92°13'55''W, 471 m, 2.3 has). Events of precipitation, direct runoff, infiltration rate and baseflow were performed. The amount, duration and intensity of rainfall events were recorded with the use of a pluviograph. Surface runoff was quantified with an established gauging station, an H-type gauging device and a horizontal mechanical gauging limnograph. Runoff base flow was measured at the gauging station using the volume-time method. Infiltration was measured using a triple ring infiltrometer, taking two measurements in the upper part and two in the lower part of the microbasin. Evapotranspiration was measured with the amount of rainfall entering and runoff leaving the watershed. In the study period, annual rainfall of 4417.6 mm distributed over 181 events were recorded;about 70% of the storms showed lower intensities at 20 mm·h-1. The total runoff was 345.8 mm caused by half of the rainfall events, which represents 7.8% of the total rain;77% of runoff events showed lower sheets of 5 mm and an average specific rate of 20.7 L·s-1·ha-1 with a maximum of 113.6 L·s-1·ha-1. Three runoff events were greater than 20.1 mm and caused the 22.5% of the total runoff depth in the study period showing the equilibrium conditions in the hydrological response of the forest. Water outputs like baseflow was 669.5 mm. In this way, 90% of the rainfall is infiltrated every year in the micro-watershed, which shows the importance of the plant cover in the hydrological regulation and the groundwater recharge.

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。

人工湿地技术对水源地雨水径流污染阻控的应用研究

设置了不同基质(砾石、加气混凝土)及是否种植美人蕉的不同人工湿地结构,通过小试实验对比各个工况对雨水径流污染的阻控效果.研究发现,加气混凝土与种植美人蕉的人工湿地组合成本略高(4.20元/工况),较其余工况高出1.00~2.90元/工况,但在运行的两个周期(交替运行30 h,落干48 h)内,NH_(4)^(+)-N、NO_(3)^(-)-N、TN、PO_(4)^(3-)、TP和COD_(Cr)的平均去除率分别为73.3%、47.0%、85.4%、56.4%、76.0%和65.5%,平均高出其余工况10.9%~18.8%,效果最优,性价比最高,适于推广应用.

昆仑山北坡水资源科学考察初报

2021年10月首批启动了第三次新疆科学考察——“昆仑山北坡水资源开发潜力及利用途径科学考察”。结合多源遥感信息和2022—2023年野外科考工作,对昆仑山北坡的水文水资源变化和水资源利用进行了调查研究。结果表明:(1)1990—2020年,昆仑山北坡山区的气温、降水分别以0.14℃·(10a)^(-1)和6.53 mm·(10a)^(-1)幅度增加。(2)冰川变化相对稳定,积雪面积和积雪深度表现为略微增加。(3)永久性水体和季节性水体面积分别显著增加79.89%和144.49%。(4)东昆仑-库木库里盆地的阿牙克库木湖和阿其克库勒湖两大湖泊的水域面积分别增加了68.91%和58.22%,盆地内多条河流具备水资源开发潜力。(5)昆仑山北坡陆地水储量总体呈增加趋势,表现为从西向东增加趋势越加显著。(6)昆仑山北坡的主要河流和田河、克里雅河和车尔臣河年均径流量2010—2023年较1957—2023年分别增加了20.24%、27.85%和45.17%。(7)基于不同气候变化情景模拟预测至21世纪中后叶,主要河流径流量将保持上升态势,区域水资源量总体呈增加趋势。昆仑山北坡的水资源禀赋可为区域绿色高质量发展提供有利的水资源保障条件。

永定河流域生态补水绩效分析及生态调度方案评估

为分析生态补水对河道内生态需水量的满足程度,以永定河流域三家店以上流域为研究区域,利用流量历时曲线法计算了不同需求条件下的河道内生态需水量,明确了现状水文条件下的河道生态缺水程度,评估了2019年和2020年生态补水过程中河道主要断面收水率及沿途损耗的空间分布规律,定量评估了生态补水对官厅水库入库流量的贡献,构建了生态水量调度模拟模型,通过对不同生态补水情景河道生态水量调度过程模拟分析,推荐了合理的生态补水调度方案.结果表明:现状永定河山区主要控制断面生态水量处于较为严重的亏缺状态,尤其是山区总控制站三家店缺水率达97%,沿途输水损耗率变化范围为(0.94%~5.38%)/10 km,且呈现上游至下游河段依次减少的规律,收水率与上游补水量呈正相关关系,构建的生态水量调度模型在两个断面率定期和验证期纳什效率系数为0.67~0.96,能够反映永定河河道生态补水过程的水流运动.根据不同情景河道生态水量调度过程模拟结果,为达到低生态流量需求目标,可采用生态补水情景方案4;为达到高生态流量需求目标,可采用生态补水情景方案5.研究成果对认识跨流域调水影响下中国北方季节性河道的生态流量恢复过程具有重要的科学意义,可为面向生态水量恢复目标的永定河跨流域调水与流域内生态补水方案制定等提供科技支撑.

工程堆积体产流产沙及水沙效益对植被近地表特征的响应

针对陡坡工程堆积体水土流失严重的问题,通过野外模拟降雨试验开展植被不同近地表特征对堆积体产流产沙和蓄水减沙效益特征影响的定量研究。选择土石混合堆积体(10%砾石质量分数,坡度30°)作为工程侵蚀下垫面的典型代表,并以裸坡(bare slope,BS)为对照,定量分析了植被在3种近地表特征条件下(完整植株(intact grass,IG),不含叶(not leaf,NL),只含根系(only root,OR)对堆积体产流产沙特征和蓄水减沙效益影响。结果表明:1)植被在IG条件下延缓坡面径流发生使其较BS滞后,效益达50.74%~188.98%,但不完整植被(NL、OR)会加速径流发生使其较BS提前2.19%~70.12%;2)植被在NL和OR下的瞬时径流率比IG增大0.20%~185.58%,在降雨强度1.8 mm/min的瞬时径流率甚至比BS高1.20%~169.10%;植被在IG和NL条件下瞬时侵蚀速率比BS减少0.91%~98.71%,但在降雨强度达到1.8 mm/min时OR条件下甚至增大侵蚀使其比BS高6.76%~75.63%;3)随降雨强度增大,植被在NL和OR条件下的减沙效益由95.18%和68.31%分别递减至46.58%和-68.13%,但对IG下的减沙效益影响小(效益差异<2%),平均蓄水效益随降雨强度增大而减小。不同堆积体水沙呈显著线性相关(R^(2)在0.40~0.88),且径流率达到4 L/min会显著改变植被对堆积体坡面防护效益。提出开展堆积体生态修复时选择冠层丰富的植被,同时要避免外部因素对植被造成损害。研究结果对于揭示植被防护扰动边坡侵蚀机制具有重要意义,可为堆积体植被修复提供实践指导。