Research on runoff variations based on wavelet analysis and wavelet neural network model： A case study of the Heihe River drainage basin （1944-2005）

The Heihe River drainage basin is one of the endangered ecological regions of China. The shortage of water resources is the bottleneck, which constrains the sustainable development of the region. Many scholars in China have done researches concerning this problem. Based on previous researches, this paper analyzed characteristics, tendencies, and causes of annual runoff variations in the Yingluo Gorge （1944-2005） and the Zhengyi Gorge （1954-2005）, which are the boundaries of the upper reaches, the middle reaches, and the lower reaches of the Heihe River drainage basin, by wavelet analysis, wavelet neural network model, and GIS spatial analysis. The results show that： （1） annual runoff variations of the Yingluo Gorge have principal periods of 7 years and 25 years, and its increasing rate is 1.04 m^3/s.10y; （2） annual runoff variations of the Zhengyi Gorge have principal periods of 6 years and 27 years, and its decreasing rate is 2.25 m^3/s.10y; （3） prediction results show that： during 2006-2015, annual runoff variations of the Yingluo and Zhengyi gorges have ascending tendencies, and the increasing rates are respectively 2.04 m^3/s.10y and 1.61 m^3/s.10y; （4） the increase of annual runoff in the Yingluo Gorge has causal relationship with increased temperature and precipitation in the upper reaches, and the decrease of annual runoff in the Zhengyi Gorge in the past decades was mainly caused by the increased human consumption of water resources in the middle researches. The study results will provide scientific basis for making rational use and allocation schemes of water resources in the Heihe River drainage basin.

Effectiveness of urban distributed runoff model for discharge and water depth calculation in urban drainage pipe networks

Effective urban land-use re-planning and the strategic arrangement of drainage pipe networks can significantly enhance urban flood defense capacity.Aimed at reducing the potential risks of urban flooding,this paper presents a straightforward and efficient approach to an urban distributed runoff model(UDRM).The model is developed to quantify the discharge and water depth within urban drainage pipe networks under varying rainfall intensities and land-use scenarios.The Nash efficiency coefficient of UDRM exceeds 0.9,which indicates its high computational efficiency and potential benefit in predicting urban flooding.The prediction of drainage conditions under both current and re-planned land-use types is achieved by adopting different flood recurrence intervals.The findings reveal that the re-planned land-use strategies could effectively diminish flood risk upstream of the drainage pipe network across 20-year and 50-year flood recurrence intervals.However,in the case of extreme rainfall events(a 100-year flood recurrence),the re-planned land-use approach fell short of fulfilling the requirements necessary for flood disaster mitigation.In these instances,the adoption of larger-diameter drainage pipes becomes an essential requisite to satisfy drainage needs.Accordingly,the proposed UDRM effectively combines land-use information with pipeline data to give practical suggestions for pipeline modification and land-use optimization to combat urban floods.Therefore,this methodology warrants further promotion in the field of urban re-planning.

A subsurface runoff parameterization with water storage and recharge based on the Boussinesq-Storage Equation for a Land Surface Model

Subsurface runoff in a land surface model is usually parameterized as a single-valued function of total storage in a basin aquifer reservoir. This kind of parameterization is often sin-gle-valued function of storage-discharge under a steady or “quasi-steady” state, which cannot rep-resent the influence of aquifer recharge on subsurface runoff generation. In this paper, a new sub-surface runoff parameterization with water storage and recharge based on the Boussinesq-storage equation is developed. This model is validated by a subsurface flow separation algorithm for an ex-ample river basin, which shows that the new model can simulate the subsurface flow reasonably.

Effect of Drainage Ditch Layout on Nitrogen Loss by Runoff from an Agricultural Watershed

A comparison experiment was performed, by designing one field ditch （D1 treatment）, two field ditches （D2 treatment）, three field ditches （D3 treatment）, and no field ditch （CK treatment）, in an upland of a small agricultural watershed in Nanjing-Zhenjiang hilly regions to observe the farmland surface runoff and N loss characteristics under the different layouts of field ditch. As the layout density of field ditch increased, the drainage effect was improved, the timing of the runoff peak was advanced, and also the peak flow was augmented. At the same time, both the concentration and accumulated transfer flux of total nitrogen （TN） were improved, and thereinto the accumulated transfer fluxes of TN under D3, D2 and D1 treatments were increased by 1.46, 1.34 and 1.16 times, respectively, than that under CK treatment. However, the accumulated transfer fluxes of nitrate-nitrogen （NO3-N） and ammonium-nitrogen （NH4＋-N） under D3, D2 and D1 treatments were reduced by 33.9%, 21.4% and 8.6%, and 35.8%, 24.7% and 12.2%, respectively, compared with those under CK treatment. Under CK treatment, the NO3-N and NH4＋-N concentrations were more sensitive to rainfall intensity than the TN concentration. There were significant linear relationships between the transfer fluxes of TN, NO3-N and NH^-N and the runoff flux, with the correlation coefficients of 0.942, 0.899 and 0.912, respectively. In addition, this correlation was also influenced by the layout density of field ditch. Therefore, the environmental effect should be taken into account when designing and constructing field ditches. Especially in the regions of severe fertilizer loss, the approaches of properly increasing the drainage area and decreasing the layout density of field ditch could be adopted under the precondition of avoiding crops from waterlogging.

Calibration of SWAT2009 Using Crop Biomass, Evapotranspiration, and Deep Recharge: Calera Watershed in Zacatecas, Mexico Case Study

Groundwater is the main source of water in the semi-arid Calera watershed, located in the State of Zacatecas, Mexico. Due to increasing population, rapid industrial growth, and increased irrigation to meet growing food demand, groundwater extraction in the Calera watershed are exceeding recharge rates. Therefore, development and evaluation of alter-native water management strategies are needed for sustainable development of the region. The Soil and Water Assessment Tool (SWAT) model was selected for this purpose as it has been used to simulate a wide range of agricultural production, the extensive testing and application in diverse watersheds worldwide, and the potential for future linkage of this model to groundwater models. However, crucial flow data which are commonly used for calibrating hydrologic models are not available in this watershed. This paper describes a novel calibration methodology that uses biomass and water balance approach which has potential for calibration of hydrologic models in ungauged or data-scarce watersheds, which are prevalent in many parts of the world. Estimated long-term annual average actual evapotranspiration (AET), and deep aquifer recharge rates and plant biomass values based on the expert knowledge of researchers and managers in the watershed were used as targets for calibration. The model performance was assessed using the Nash-Sutcliffe effi-ciency coefficient (NSE), coefficient of determination (R2), and percent bias (PBIAS, %) statistics. On average, the calibrated SWAT model yielded annual Nash-Sutcliffe efficiency coefficient values of 0.95, 0.99, and 0.85 for AET, recharge, and biomass, respectively. The coefficient of determination, values for AET, recharge, and biomass were 0.95, 0.94, and 0.99 respectively. The percent bias values of ±2.21%, ±0.18%, and ±0.96% for AET, recharge, and biomass, respectively, indicated that the model reproduced the calibration target values of the three water budget variables within an acceptable value of ± 10.0%. Therefore, it is concluded that the calibrated SWAT model can be used in evaluating alternative water management scenarios for the Calera watershed without further validation. Considering the relative ease in developing calibration data and excellent performance statistics, the calibration methodology proposed in this study may have the potential to be used for ungauged or data-scare agricultural watersheds that are prevalent in many parts of the world.

Groundwater recharge rates and surface runoff response to land use and land cover changes in semi-arid environments

The effects of land use and land cover(LULC)on groundwater recharge and surface runoff and how these are affected by LULC changes are of interest for sustainable water resources management.However,there is limited quantitative evidence on how changes to LULC in semi-arid tropical and subtropical regions affect the subsurface components of the hydrologic cycle,particularly groundwater recharge.Effective water resource management in these regions requires conclusive evidence and understanding of the effects of LULC changes on groundwater recharge and surface runoff.We reviewed a total of 27 studies(2 modeling and 25 experimental),which reported on pre-and post land use change groundwater recharge or surface runoff magnitude,and thus allowed to quantify the response of groundwater recharge rates and runoff to LULC.Comparisons between initial and subsequent LULC indicate that forests have lower groundwater recharge rates and runoff than the other investigated land uses in semi-arid tropical/subtropical regions.Restoration of bare land induces a decrease in groundwater recharge from 42% of precipitation to between 6 and 12% depending on the final LULC.If forests are cleared for rangelands,groundwater recharge increases by 7.8±12.6%,while conversion to cropland or grassland results in increases of 3.4±2.5 and 4.4±3.3%,respectively.Rehabilitation of bare land to cropland results in surface runoff reductions of between 5.2 and 7.3%.The conversion of forest vegetation to managed LULC shows an increase in surface runoff from 1 to 14.1% depending on the final LULC.Surface runoff was reduced from 2.5 to 1.1% when grassland is converted to forest vegetation.While there is general consistency in the results from the selected case studies,we conclude that there are few experimental studies that have been conducted in tropical and subtropical semi-arid regions,despite that many people rely heavily on groundwater for their livelihoods.Therefore,there is an urgent need to increase the body of quantitative evidence given the pressure of growing human population and climate change on water resources in the region.

Soil water movement and deep drainage through thick vadose zones on the northern slope of the Tianshan Mountain: Croplands vs.natural lands

Regional aridity is increasing under global climate change,and therefore the sustainable use of water resources has drawn attention from scientists and the public.Land-use changes can have a significant impact on groundwater recharge in arid regions,and quantitative assessment of the impact is key to sustainable groundwater resources management.In this study,the changes of groundwater recharge after the conversion of natural lands to croplands were investigated and compared in inland and arid region,i.e.,the northern slope of the Tianshan Mountain.Stable isotopes suggest that soil water in topsoil(<2 m)has experienced stronger evaporation under natural lands than croplands,and then moves downward as a piston flow.Recharge was estimated by the tracer-based mass balance method,i.e.,chloride and sulfate.Recharge rates under natural conditions estimated by the chloride mass balance(CMB)method were estimated to be 0.07 mm/a in deserts and 0.4 mm/a in oases.In contrast,the estimated groundwater recharge ranged from 61.2 mm/a to 44.8 mm/a in croplands,indicating that groundwater recharge would increase significantly after land changes from natural lands to irrigated croplands in arid regions.Recharge estimated by the sulfate mass balance method is consistent with that from the CMB method,indicating that sulfate is also a good tracer capable of estimating groundwater recharge.

Seasonal evolution of the englacial and subglacial drainage systems of a temperate glacier revealed by hydrological analysis

Englacial and subglacial drainage systems of temperate glaciers have a strong influence on glacier dynamics, glacier-induced floods, glacier-weathering processes, and runoff from glacierized drainage basins. Proglacial discharge is partly controlled by the geometry of the glacial drainage network and by the process of producing meltwater. The glacial-drainage system of some alpine glaciers has been characterized using a model based on proglacial discharge analysis. In this paper, we apply cross-correlation analysis to hourly hydro-climatic data collected from China＇s Hailuogou Glacier, a typical temperate glacier in Mt. Gongga, to study the seasonal status changes of the englacial and subglacial drainage systems by discharge-temperature （Q-T） time lag analy-sis. During early ablation season （April-May） of 2003, 2004 and 2005, the change of englacial and subglacial drainage system usually leads several outburst flood events, which are also substantiated by observing the leakage of supraglacial pond and cre-vasses pond water during field works in April, 2008. At the end of ablation season （October-December）, the glacial-drainage net-works become less hydro-efficient. Those events are evidenced by hourly hydro-process near the terminus of Hailuogou Glacier, and the analysis of Q-T time lags also can be a good indicator of those changes. However, more detailed observations or experi-ments, e.g. dye-tracing experiment and recording borehole water level variations, are necessary to describe the evolutionary status and processes of englacial and subglacial drainage systems evolution during ablation season.

THE COMPARISON OF CHINESE AND EUROPEAN STREAM RUNOFF

This paper compares stream stream runoff in China in terms of drainage basin, water balance, and regional distribution and regime of stream runoff with that in Europe. European stream runoff resources are more abundant than that of China. Europe has 28 rivers with runoff volume exceeding 10 km3, and China only has 19.But Europe has no rivers like those in China which are long andhave abundant waer volume such as Changiiang (Yangtze River) and Zhujiang. Heat conditions of the European water-abundant and water-sufficient zones are poor and their agiculture are not flourishing.In China these zones have very good heat conditions and are main farm production regions. The interannual and annual variation of stream runoff are the sane to the irrespective feedings in Europe and China.

Indigenous Knowledge and Techniques of Runoff Harvesting (Bandsar and Khooshab) in Arid and Semi Arid Regions of Iran

Two-thirds of Iran’s landmass is considered a desert-land devoid of forests and green pastures. Such a harsh environmental condition ancient Iranian innovated amazing techniques and knowledge for supplying water, which are recently called indigenous knowledge. Rain water and runoff harvesting techniques are often applied to increase the water recharge and consequently productivity in arid regions. The sizes of runoff harvesting structures are varying form micro to macro landscape. Qanat, Khooshab, Bandsar and Degar are the most famous indigenous techniques of water resources management in Iran. We tried to introduce two methods (Bandsar and Khooshab), their classification and structure as well as benefits. Bandsar is a kind of flood farming structure ground water recharge prevailed in Khorasan province of eastern Iran. Depending on rainfall, land topography and geomorphology of area, different types have been established to use floods and agricultural activities. Their area is about 0.5 to 5 ha in alluvial fans and piedmont plain. Its structure consists of plots, basin and levee along contour lines and dry rivers. The upland generated runoff is stored in the basin to infiltrate. Moreover, the fine trapped sediment in Bandsar as a fertile material cause to improve sandy soils. Khooshab is another traditional method used in southeast of Iran (Sistan va Baluchistan). It is a wall structures built across or along the dry river to catch the summer Monson floods water and cultivation as well as combat to wind erosion. Their areas are about 1 - 10 ha and crops such as wheat, maize and barely are produced through them. Flood plains and piedmont are the best location for Khooshabs which caused aquifer recharging. This work tries to explain about environmental condition affect the outcomes of mentioned techniques and their side effects on decreasing soil erosion, flooding and desertification as well as productivity increasing in some parts of Iran. Our findings revealed that the efficiency of traditional knowledge is closely integrated with environment conditions and socio-economic situation of rural community such as participatory. However, they can act as a good alterative in conjunction of new technological methods.

Watershed Delineation and Estimation of Groundwater Recharge for Ras Gharib Region, Egypt

The present work tried to estimate the runoff discharge and groundwater recharge volumes for the catchments of Ras Gharib area using the Soil Conservation Service curve number (SCS-curve number) and the water balance methods. The two methods were selected among other methods used by hydrologists due to simplicity and popularity for application in arid and semi-arid areas like Egypt. The watershed delineation and streamlines for Ras Gharib region have been accomplished using ArcMap 10 GIS and the 1-arc second DEM which demonstrated three basins in the study area. The rainfall data points nearby the study area, extracted from the TRMM data, have been used as input for the Log-Pearson III distribution in order to calculate the design storm for different return periods (100, 50, 25, and 10 years). The results of applying the SCS model estimated the runoff depths as 19.86, 8.00, 2.32, and 0.06 mm for the different return periods, respectively. The total surface runoff volumes reached the study area are 34.78, 14.02, 4.07, and 0.11 Mm3, respectively for the selected return periods, whereas the total groundwater recharge volumes for the selected storm return periods are 58.16, 31.34, 18.14, 3.18 Mm3, respectively.

A GIS-Based Modelling for Identifying High Priority Areas for Groundwater Recharge

At semi-arid areas that dominant portion of required water for agriculture is provided by exploitation of groundwater,these resources encounter with more deterioration.Thus identifying of potential runoff generating sites and estimation of runoff depth can be a significant step for storing runoff for agricultural activities and groundwater recharge.The main purposes of this study are use of GIS(geographic information system)ability for identifying of potential runoff generating sites,and thus identifying high priority areas for groundwater recharge in the Gharehchay River watershed in the north of Hamedan province,Iran.Potential runoff generating sites were identified by using watershed features same as slope,land use and hydrological soil groups.Afterward,CN I(Curve Number I)technique,which is one of the eight derivations of the NRCS-CN(natural resources conservation services curve number)method,was utilized to calculate rainfall-runoff depth in the study region.Finally,map layers were ranked in order of highest priority to lowest priority,based on the criteria of each dataset,and high priority areas for groundwater recharge were identified by integrating potential runoff map,runoff depth and depth to groundwater maps.Spatial analysis revealed that 51%of the study region has a high priority for groundwater recharge.

The Drainage Exchange of Stormwater Potential in Flat Area Problems

Groundwater as an alternative source still does not contribute to the water supply in area of Parit Raja because of the limitation of water availability in the ground. This lacking of groundwater could be caused by the circumstance that the top layer of soil is dominated by compacted clay around 2 meters in which its permeability is small, so the water is difficult to infiltrate the ground. The recharge well technique was designed based on the flat area problems, layer of real condition, flow water table and low infiltration rate. Resistivity soundings were made at existing wells to assess the subsurface layers. Beside that, the past records on floods event, sub surface and surface studies were collected around study area as a preliminary studies. It was presented that the study area promised good prospects to increase the capability of groundwater and contribute to the drainage system by reducing the volume of rainfall runoff using the recharge well technique.

Basin Groundwater Recharge and Discharge in the Gully Erosion Prone Areas of Anambra, Nigeria

Anambra State of Nigeria is ravaged by ecological hazards of gully erosion and landslides. Over 450 active gully and landslide sites with depths ranging from 5 m to over 120 m are concentrated on both sides of the Awka-Nanka-Umuchu-Orlu cuesta. The Idemili River and Odo River form the major drainage basins of the area. The geomorphic characteristic of the cuesta/escarpment is a major controlling factor in groundwater recharge and discharge within the drainage basins. Rise in aquifer levels result in hydrogeotechnical implications of gully development and landslides. The calculated values of hydraulic properties of conductivity and transmissivity range from 1.20×10^-1 to 5.93×10^-1 cm/s and 1.15×10^5-13.05×10.3 m^2/s respectively. The values of groundwater velocity and groundwater discharge were 82 m.yearl and 2.96×10^6 m^3.yearl The plasticity index of the soil in the gully prone areas is relatively low ranging from 12.50-36.57%. The unique features of the geologic formations together with obtained aquifer characteristics favour gully/landslide hazards in the area.

Influence of Land Use Land Cover Change on Groundwater Recharge in the Continental Terminal Area of Abidjan,Ivory Coast

The process by which rainfall reaches the aquifer in a sedimentary area is infiltration. This process could be affected quantitatively or qualitatively by the changes in the land use land cover (LULC) as a result of anthropogenic activities which could affect groundwater reserves. This study focuses on the influence of LULC change on groundwater recharge in the context of urbanization and population growth. Four weather stations data and satellite image data were used in order to evaluate water infiltration which is the amount of water that reaches the piezometric surface from 1990 to 2016. The spatial-temporal LULC change in relation to urbanization sprawl was assessed based on a series of Landsat images for 1990, 2000 and 2016. The maximum likelihood pixel-based on classification method was used to analyze the spatial-temporal LULC dynamics. The Thiessen polygon method was used for the mean area precipitation computation. The recharge was determined using water balance method after determining the runoff based on the Soil Conservation Service curve number method. The results show an increase in built-up and agricultural land, while the forest and shrub areas declined with water body remaining unchanged over the period 1990-2016. The decline in forest could be imputed to the demographic and socio-economic growth as expressed by the expansion of agriculture and urbanization. Groundwater recharge and runoff results are respectively 34%, 20% in 1999;21%, 46% in 2000 and 26%, 14% in 2016 of rainfall and show their strong dependence on precipitation and LULC change.

STORM WATER BEST MANAGEMENT PRACTICES THAT MAXIMIZE AQUIFER RECHARGE

This article reviews and provides evaluation guidelines for six major storm water best management practices includingbioretention areas, grassed swales/fi lter strips, infi ltration trenches, porous pavement, rain barrels and wet detentionponds. A detailed table allows for quick and easy design comparisons, including a separate table which allows forsite specifi c cost comparisons. A logic diagram is provided as a basic tool for screening the most feasible managementpractice.

Research on the conversion relationships between the river and groundwater in the Yellow River drainage area

Conversion relationships between the river and groundwater in the Yellow River drainage area are studied in this paper based on the geologic and physiognomy conditions and the data of the groundwater regime, isotope, groundwater flow field and field survey. Then eight recharge and discharge modes on the relationships are put forward and the hydraulic characteristics of the modes are analysed, which provides a scientific basis for quantitatively simulating and assessing the conversion relationships, maintenance mechanism of the Yellow River and the regeneration ability of the groundwater in the area.

Water-saving irrigation of paddy field to reduce nutrient runoff

The purpose of this work is to study the effect of a type of water-saving irrigation （WSI） on nutrient runoff of paddy field. The volume of surface drainage was maintained low by WSI. In particular, WSI effectively reduced surface drainage in rain events. Model simulation indicated that net runoff load of total nitrogen （TN） from the paddy field was increased by WSI. Meanwhile, net runoff loads of total phosphorus （TP） and total organic carbon （TOC） from the paddy field was decreased by WSI. Because ponding waters of the study fields were enriched with TP and TOC, WSI reduced runoff of these nutrients by controlling the volume of surface drainage. WSI could be considered an efficient method for reducing runoff loads and could conserve water quality in an agricultural watershed.

森林结构差异对大兴安岭森林小流域径流情势和退水特征的影响

径流情势和流域退水是反映水文过程至关重要的指标,除气候因素外,主要受到下垫面和流域水文地质特征的影响。利用准配对流域法,对比大兴安岭地区森林结构不同的2个小流域(老爷岭流域、圣诞村流域),排除气候和地形地貌的干扰,探究森林结构变化对流域径流情势及退水过程的影响。结果表明:老爷岭流域的全年洪峰历时比圣诞村流域延长5 h、平均洪峰滞时推迟2 h,洪峰径流量、变异系数均无显著差异。随着森林平均蓄积量、树种组成、郁闭度等森林结构指标的提高,老爷岭流域(森林结构综合指数较高)较圣诞村流域(森林结构综合指数低)的枯水径流时间低4 h,平均枯水径流深提高0.65 mm(是圣诞村流域3倍),平均枯水径流变异系数低33%,且流域间差异均达到了极显著水平(P<0.01)。通过退水分析,结果表明:老爷岭流域和圣诞村流域退水系数(k)的均值分别为16.9、8.5 d,退水常数(α)均值分别为0.909 4、0.862 6,老爷岭流域的平均退水时间比圣诞村流域延缓了8.4 d。该地区流域水文特征受森林植被变化的影响明显,森林结构复杂、森林质量高的老爷岭流域枯水径流量高并且稳定,退水过程更慢,水源涵养功能更好。

北方岩溶区降水入渗补给系数及补给机制:以羊庄岩溶水系统为例

为建立北方岩溶区水文地质参数系列,提高岩溶地下水可采资源计算精度,笔者团队于20世纪80年代开始,在山东羊庄封闭式泉排型岩溶水系统开展了岩溶水均衡试验研究,积累了40余年的监测试验数据。根据长期野外水均衡要素观测资料,推导出裸露型、半覆盖型和覆盖型岩溶区降水入渗补给系数计算公式,建立了岩溶区降水入渗补给系数α与降水量P和地下水位埋深D的相关方程,以及可调控的最大降水入渗补给系数系列,揭示了降水入渗补给过程与α变化机制。结果表明:α随水位埋深D的改变而改变,每个降水量P段分别对应一个最大降水入渗补给系数α_(max)和最大降水入渗补给量即补给极限G_(max),相应的水位埋深便是最佳水位埋深D_(critical)。D>D_(critical)时,包气带截留量随着水位埋深的增大而增大,α<α_(max);D<D_(critical)时,地表径流量随着地下水位埋深的减小而增大,α<α_(max)。不同的降水量段对应不同的D_(critical),降水量增大时,对应的α_(max)及D_(critical)也增大。在任意水位埋深时,G_(max)为蓄满产流临界降水量与包气带最大截流量之差。本研究解决了岩溶区降水入渗补给的关键科学问题,即揭示降水入渗补给机制、建立降水入渗补给系数与降水量和水位埋深的定量关系,提升了我国北方岩溶水资源基础性研究水平。