Assessment of Rainwater Availability by Building Type and Water Use Through GIS-based Scenario Analysis

Scenario analysis of rainwater harvesting and utilization (RWHU) was performed considering various non-potable water uses in different building types over a year. Six building types were identified in the study area using GIS data: residential houses, offices, commercial buildings, restaurants, public buildings, and “others”. Rainwater storage capacity was considered as 30 mm rainwater depth. Water demand for each building type was calculated as the sum of the individual water uses for toilet flushing, air conditioning, garden irrigation, and cleaning defined in this study as “miscellaneous usages”. To incorporate water quality considerations, rainwater with suspended solids level of less than 2 mg l⁻¹ was used as the quality criterion. The RWHU scenario was compared with other storage and water use scenarios. This study quantified the rainwater availability throughout a year and its seasonal variation and consumption in each building type. The analysis clarified the effectiveness of rainwater utilization for supplementing existing water resources.     

Effectiveness of Rainwater Harvesting in Runoff Volume Reduction in a Planned Industrial Park,China

It is urgent to effectively mitigate flood disasters in humid mountainous areas in southeastern China for the increasing flood risk under urbanization and industrialization. In this study, a rural district with an area of 13.39 km² that planning to build an industrial park covering an area of 7.98 km² in Changting was selected to estimate the potential of collectable rainwater and the extent to which runoff volume can potentially be mitigated by rainwater harvesting. In addition, the optimum cistern capacity of a rainwater harvesting system in the planned industrial park was evaluated using daily water balance simulation and cost-efficiency analysis. The results showed that rainwater harvesting in the planned industrial park has great potential. The annually collectable rainwater is approximately 9.8?×?10⁶ m³ and the optimum cistern capacity is determined to be 0.9?×?10⁶ m³. With the optimum cistern capacity, the annual rainwater usage rate is 0.99, showing neither financial savings nor deficits. Rainwater harvesting can reduce 100 % of runoff volume in the cases of critical rainfall storm (50 mm) and annual average maximum daily rainfall (111.2 mm), and 58 % of runoff volume in the case of maximum daily rainfall (233.6 mm), respectively. All surface runoff can be collected and stored in the cisterns when rainfall amount is less than 135.5 mm in a rainstorm event.     

Assessments of Impacts of Climate Change and Human Activities on Runoff with SWAT for the Huifa River Basin,Northeast China

The impacts of climate change and human activates on the runoff for Huifa River Basin, Northeast China, have been investigated with the soil and water assessment tool (SWAT), which is calibrated and verified for the baseline period 1956–1964, and then used to reconstruct the natural runoff from 1965 to 2005. The results indicate that both climate change and human activities are responsible for the decrease of observed runoff in Huifa River. The climate change could result in a decrease or increase of runoff depending on precipitation, temperature, radiation variation, as well as land cover changes. Its impacts on annual runoff are -36.7, -59.5, +36.9 and -45.2 mm/a for 1965–1975, 1976–1985, 1986–1995 and 1996–2005, respectively, compared with the baseline period 1956–1964. Human activities, on the other hand, generally lead to a decrease of runoff and a relatively larger magnitude than climate change after 1985. It has decreased the annual runoff by -32.9, -46.8, -67.8 and -54.9 mm/a for 1965–1975, 1976–1985, 1986–1995 and 1996–2005, respectively. Human activities contributed more to runoff decrease in wet years due to regulation and storage of the water projects. The results of this study could be a reference for regional water resources management since there are quite a number of reservoirs in the Huifa River basin.     

A Distributed Kinematic Wave–Philip Infiltration Watershed Model Using FEM,GIS and Remotely Sensed Data

Distributed rainfall–runoff modeling is very important in the water resources planning of a watershed. In this study, a kinematic wave based distributed watershed model which simulates runoff on an event basis has been presented here. The finite element method (FEM) has been used to simulate the overland runoff and channel flow. Philip model has been used for the infiltration estimation. To find out runoff at the outlet of the watershed, both overland flow and channel flow models are coupled. The coupled model has been applied to a typical Indian watershed. Remotely sensed data has been used to obtain the land use (LU)/land cover (LC) for the watershed. Slope map of the watershed has been obtained using geographical information systems (GIS). The grid map of the watershed which contains overland flow elements connecting to channel flow elements has been prepared in GIS. The elemental input files such as slope and Manning’s roughness are prepared using the GIS and are directly used in the model. The model has been calibrated using some of the rainfall events and validated for some other events. The model results are compared with the observed data and found to be satisfactory. A sensitivity study of the infiltration parameters, overland and channel flow Manning’s roughness and time step has also been carried out. The developed model is useful for the simulation of event based rainfall–runoff for small watersheds.     

An Optimization Approach for Assessing the Reliability of Rainwater Harvesting

This study was aimed at developing an optimization approach to rainwater harvesting (RWH) considering three (3) water consumption scenarios (WCS). These scenarios which include basic water need (BWN), pour flush (PF) and full plumbing connection (FPC) corresponding to 50 litres per capita per day (lpcd), 75(lpcd) and 150(lpcd) respectively were simulated for different categories of buildings. Reliability of supply was determined by first obtaining composite surplus/deficit of rainwater followed by optimizing the redistribution of surplus rainwater harvested to deficient buildings. Results showed that when total annual rainfall intercepted by roof exceeded total demand, 100% reliability of water supply was guaranteed. Reliability was found to be a linear function of storage. When reliability of supply is possible, the optimized storage bears an inverse exponential relationship to the roof plan area per capita. The relationship between surplus/deficit and roof plan area per capita follows a one-phase decay pattern. An optimal redistribution of surplus water from self-sufficient buildings to deficient ones gave an improvement in supply reliability from 64 to 87% for basic water need, 47 to 58% for pour flush and 28 to 29% for full plumbing connection.     

区域雨水资源化潜力计算及时空分布规律研究

为充分利用雨水资源应对区域水资源紧缺问题,以黑龙江省松嫩平原为研究区,考虑地下水补给量和基流量对雨水资源化潜力的影响,引入分布式水文模型SWAT,提出了适用于研究区的雨水资源化潜力计算模型,计算了研究区的雨水资源化潜力,分析了研究区雨水资源化潜力时空分布规律。结果表明:研究区雨水资源化潜力在时间和空间上均存在一定差异,各分区之间以及同一分区不同年份雨水资源化潜力及其构成也存在较大的差异;生育期多年平均可利用雨水资源化潜力为343.78亿m~3,占生育期多年平均雨水总量的50.28%;各分区产流量在雨水资源化潜力中占比均较大,建议要注重提高降水径流汇集、径流蓄存和集雨补灌等相关技术;在土壤水增量占比大的分区要注重节水灌溉技术的应用。总体来看,黑龙江省松嫩平原地区雨水资源化潜力巨大,应该科学合理提高雨水资源利用率,保障区域农业可持续发展。     

Runoff Efficiency and the Technique of Micro-water Harvesting with Ridges and Furrows,for Potato Production in Semi-arid Areas

A field study was conducted to determine runoff efficiency and the effects of different ridge: furrow ratios and ridge-covering materials on tuber yield, soil moisture storage and water use efficiency (WUE) in the ridge and furrow micro-water harvesting system in a dry semi-arid region of China, during two consecutive years of 2002 and 2003. The average runoff efficiency of ridges with compacted soil (SR) was very low (24.6–28.8%) compared to that of ridges covered with plastic film (MR) (91.1–94.3%). The minimal rainfall necessary to produce runoff was 2.76–2.78 mm for SR, only 0.23–0.47 mm for MR. The field experiments using potato as an indicator crop showed that tuber yields in the MR system were significantly higher than that in the flat planting (control), with an average increase of 158.6–175.0% during 2 years. In the SR system, the average increase was valued of 14.9–28.4% during 2 years. Regression analysis between tuber yields and ridge widths indicated the optimum ridge: furrow ratio for MR was 39: 60 cm in 2002 and 48: 60 cm in 2003 respectively. The WUE values of potato in MR were 1.50 times greater than that of the controls in 2002 and 1.62 times greater than the controls in 2003. No differences were found in the WUE between the SR and the controls on average of 2 years. Due to the different runoff efficiency between two ridge-covering materials and absence of runoff occurrence in the controls, the soil water content in the MR was higher than that in the SR, both of which were greater than the controls. With the soil crust development, the distribution of soil water at the bottom of the furrow, at the side of the furrow and at the top of the ridge, is similar between the SR and the MR.     

Maximum Grade Approach to Surplus Floodwater of Hyperconcentration Rivers in Flood Season and its Application

The severe soil erosion in the Chinese Loess Plateau has resulted in a considerable wastage of surface runoff (floodwater) in flood season due to high sediment concentration in runoff. To address the water scarcity problem, it is a viable solution to utilize the floodwater. A maximum grade approach (MGA) is presented to calculate the coefficient of surplus floodwater in flood season. The raw data sequences are analyzed in a four-step process. An upper triangle of grades is obtained after the third step. A relationship between coefficient of surplus floodwater and sediment concentration in runoff is achieved in terms of the upper triangle. The surplus floodwater in flood season then can be determined. A case study of water diversion from the Jinghe River (the second tributary of the Yellow River, China) to the Jinghuiqu Irrigation District for irrigation was performed. The monthly data sequences of runoff volume, water diversion and sediment concentration in runoff from May to September for the period 1933–2001 are employed. A 16-grade upper triangle is obtained based on the MGA. A functional relationship between the coefficient of surplus floodwater (y, %) and the sediment concentration in runoff (x, %) is achieved as y = 0.0191x + 0.1516 (R^2\thinspace = 0.9738)y = 0.0191x + 0.1516 (R^{2\thinspace } = 0.9738). Results demonstrate that the average annual surplus floodwater in flood season and available surface water resources in the Jinghe River over 69-year time span are 978 and 909 million cubic meter (mcm), respectively, when the limit of sediment concentration for river water utilization is set as 10%. The irrigation district still has a potential of available water diversion of 509 mcm over 1981–2001 time span. Compared with the traditional methods, the MGA produces more reasonable and effective results. The MGA has the ability of rapidly estimating the surplus floodwater under different limits of sediment concentration and is a useful tool for available surface water resources assessment.     

Hydrological Evolution of Wetland in Naoli River Basin and its Driving Mechanism

Naoli river basin(NRB), with an area of 24,863 km², is the largest basin and also the largest marsh distribution area in Sanjiang Plain, Heilongjiang, China. The hydrological evolution process of wetland in NRB has made a marked ecological responses for anthropic activities, also reflects the drying trend of the Sanjiang Plain, Northeast China. Global climate warming also contributes to the hydrological evolution process. The following key research results are obtained: (1) The monthly average water level of Naoli river at Caizuizi hydrological station in different ages showed a marked decline tendency, the annual mean water level dropped from 96.63 m during 1960–1969 to 95.59 m during 2000–2005, the water level drawdown is 1.04 m; (2) The annual runoff flowing into wetlands in NRB decreased. Duration of Naoli river and its tributaries being thoroughly frozen from riverbed to river-water-surface showed an prolonged trend, and the water level drawdown in frozen seasons increased. The water storage capacities of wetlands in NRB declined. (3) The interactions between ground water and surface water in wetland areas are close. The ground water level variation span is bigger than that of surface water level in wetland areas of NRB. The drawdown of ground water level promotes the surface water level to decline, correspondingly. In recent 20 years, the cultivated area extension of rice field in upstream NRB has made an adverse influence on the hydrological processes of wetlands. (4) The wetland area decrease and farmland area increase significantly contribute to the runoff depth decrease of wetlands in NRB. The runoff depth variability has been mostly posed by anthropic activities. (5) Reservoirs, ditches and dykes in NRB have greatly changed the runoff generation processes. Thickness of the seasonal frozen soil layer becoming thinner and the evaporation potential becoming bigger also contribute to the runoff depth reduction and the water level drawdown of rivers. The present study results will provide a scientific basic for developing an integrated watershed management program for NRB, especially, restoring the wetland hydrological processes, maintaining or improving the wetland structure and enhancing the wetland service functions.     

山地城市屋面雨水可利用量分析——以重庆市沙坪坝某片区为例

为定量评估山地城市屋面雨水可利用量,以重庆市沙坪坝某片区为例,分析了重庆市的降雨特征,利用改进的径流系数法定量评估了代表年屋面雨水可利用量,并分析了降雨特征对可利用量的影响;运用设计降雨量和设计暴雨强度两个指标相结合的方法确定了蓄水池规模,使其满足径流控制率和防洪减涝的要求。研究表明:在代表年降雨量为1 198.9、1 104.4和962.7 mm时,研究区域屋面雨水可利用量分别为267 951.8、247 421.3和198 917.9 m~3,雨水利用潜力较大,降雨量对可利用量的影响较大,而降雨强度对其影响很小;研究区域蓄水池总规模为9 312 m~3,屋面径流控制率达到86.4%,为山地城市雨水利用系统中蓄水池的规模设计提供了参考依据。     

Hypsometric Integral Estimation Methods and its Relevance on Erosion Status of North-Western Lesser Himalayan Watersheds

Assessment of erosion status of a watershed is an essential prerequisite of integrated watershed management. This not only assists in chalking out suitable soil and water conservation measures to arrest erosion and conserve water but also helps in devising best management practices to enhance biomass production in watersheds. The geologic stages of development and erosion proneness of the watersheds are quantified by hypsometric integral. The estimation of hypsometric integral is carried out from the graphical plot of the measured contour elevation and encompassed area and by using empirical formulae. In this study, efforts were made to estimate the hypsometric integral values of the Sainj and Tirthan watersheds and their sub watersheds in the Lesser Himalayas using four different techniques, and to compare the procedural techniques of its estimation and relevance on erosion status. It was revealed that the hypsometric integral calculated by elevation–relief ratio method was accurate, less cumbersome and easy to calculate within GIS environment. Also comparison of these hypsometric integral values revealed that the Sainj watershed (0.51) was more prone to erosion than the Tirthan watershed (0.41). Further, the validation of these results with the recorded sediment yield data of 24 years (1981–2004) corroborated that the average annual sediment yield during this period for Sainj watershed (0.53 Mt) was more than that of the Tirthan watershed (0.3 Mt). Thus, the hypsometric integral value can be used as an estimator of erosion status of watersheds leading to watershed prioritization for taking up soil and water conservation measures in watershed systems.     

雨水回用对城市水循环和下游生态环境的影响

基于水量平衡理论和城市径流污染控制理论,从水量和水质2个方面探讨城市雨水回用对地表水和地下水原有自然径流以及对下游生态环境的影响。结果表明:雨水回用不仅不会减少雨水入渗量,还可以控制雨水径流污染,削减汛期江河下游区域的洪峰流量,是改善下游区域生态环境的有效途径。最后对城市雨水回用的合理规划提出了建议。     

A Multivariate ANN-Wavelet Approach for Rainfall–Runoff Modeling

Without a doubt the first step in any water resources management is the rainfall–runoff modeling over the watershed. However considering high stochastic property of the process, many models are being still developed in order to define such a complex phenomenon in the field of hydrologic engineering. Recently Artificial Neural Network (ANN) as a non-linear inter-extrapolator is extensively used by hydrologists for rainfall–runoff modeling as well as other fields of hydrology. In the current research, the wavelet analysis was linked to the ANN concept for modeling Ligvanchai watershed rainfall–runoff process at Tabriz, Iran. For this purpose the main time series of two variables, rainfall and runoff, were decomposed to some multi-frequently time series by wavelet theory, then these time series were imposed as input data to the ANN to predict the runoff discharge 1 day ahead. The obtained results show the proposed model can predict both short and long term runoff discharges because of using multi-scale time series of rainfall and runoff data as the ANN input layer.     

Groundwater Recharge Assessment for the Kalahari Catchment of North-eastern Namibia and North-western Botswana with a Regional-scale Water Balance Model

Groundwater is the only source of drinking water for the inhabitants of the Kalahari. Thus understanding spatial and temporal variations in groundwater recharge is very important and a regional-scale water balance model has therefore been set up for a 209,149 km² catchment in north-eastern Namibia and north-western Botswana. The model has a spatial resolution of 1.5 × 1.5 km, daily model time-steps, and climatic input parameters for 19 years are used. The distributed, GIS-based, process-oriented, physical water balance model (MODBIL) used in this study considers the major water balance components: precipitation, evapotranspiration, groundwater recharge, and surface runoff/interflow. Mean precipitation for the study area is 409 mm a⁻¹, while mean actual evapotranspiration is 402 mm a⁻¹ and mean groundwater recharge is 8 mm a⁻¹ (2% of mean annual precipitation). The recharge pattern is mainly influenced by the distribution of soil and vegetation units. Groundwater recharge shows a high inter- and intra-annual variability, but not only the sum of annual precipitation is important for the development of groundwater recharge; a large amount of precipitation in a relatively short period is more important. Published independent data from the Kalahari in Namibia, Botswana and the Southern African region under similar climatic conditions are used to verify the modelling results.     

Assessing Crop Water Demand by Remote Sensing and GIS for the Pontina Plain, Central Italy

An estimation of the crop water requirements for the Pontina Plain, Central Italy, was carried out through the use of remote sensing land classification and application of a simple water balance scheme in a GIS environment. The overall crop water demand for the 700 km² area was estimated at about 70 Mm³ year^− 1, i.e. 100 Mm³ year^− 1 irrigation requirements when considering an average irrigation application efficiency of 70%. The simplest and least demanding available methodology, in terms of data and resources, was chosen. The methodology, based on remote sensing and GIS, employed only 4 Landsat ETM+ images and a few meteorological and geographical vectorial layers. The procedure allowed the elaboration of monthly maps of crop evapotranspiration. The application of a spatially distributed simple water balance model, lead to the estimation of temporal and spatial variation of crop water requirements in the study area. This study contributes to fill a gap in the knowledge on agricultural use of water resources in the area, which is essential for the implementation of a sustainable and sound water policy as required in the region for the application of the EU Water Framework Directive.     

Urban Rainwater Utilization and its Role in Mitigating Urban Waterlogging Problems—A Case Study in Nanjing, China

With the acceleration of the urbanization process, urban waterlogging problems are becoming more and more serious in Nanjing, China. In order to mitigate the urban waterlogging problems, it is necessary to reduce surface runoff from the source by rainwater harvesting and utilization. An urban residential district with an area of 0.58?km² in Nanjing was selected as the study area. Based on a large-scale topographic map data and the long term rainfall data (1951?C2008), the types of underlying surfaces were classified. The potentiality of collectable rainwater and the possibility of runoff volume reduction were calculated. The results showed that exploitation of rainwater harvesting from rooftops and other underlying surfaces has high potential. The annual collectable rainwater is approximately 372,284?m³, 314,034?m³ and 275,180?m³ under different cumulative frequency of rainfall at 20?%, 50?% and 75?%, respectively. The total capacity of cisterns under assumptions of return period of rainfall and rainfall duration with 5?years and 20?min is 11,022?m³. The cistern??s capacity which is used for roof rainwater harvesting is 4,083?m³, the cistern capacity for per unit roof area (1?m²) is 0.0267?m³. The results of the feasibility analysis of setting up above-ground cisterns showed that 55?% of the total roof areas in the study area are available for setting up cisterns. In the three building types, 16?% of the commercial building??s roof areas and 77?% of that of the residential and the ??others?? buildings are available for setting up cisterns. Urban waterlogging problems can be effectively reduced through rainwater harvesting by 13.9?%, 30.2?% and 57.7?% of runoff volume reduction in three cases of the maximum daily rainfall (207.2?mm), the average annual maximum daily rainfall (95.5?mm) and the critical rainfall of rainstorm (50?mm).     

Assessing the Potential for Rainwater Harvesting

Rainwater harvesting is one of the promising ways of supplementing the surface and underground scarce water resources in areas where existing water supply system is inadequate to meet demand. Rainwater harvesting is one of the measure for reducing impact of climate change on water supplies. Abeokuta has a mean annual rainfall of 1,156 mm which makes rainwater harvesting ideal. Intra annual variability lies betwen 0.7 and 1.0 while the inter annual variability was 0.2. Annually 74.0 m³ of rainwater can be harvested per household. Estimated annual water demand for flushing, laundry and flushing were 21.6 and 29.4 m³ respectively. Harvested rainwater in Abeokuta can satisfy household monthly water demand for WC flushing and laundry except for November, December, January and February. The excess rainwater stored in September and October is sufficient to supplement the short fall in the dry months provided there is adequate storage.Water savings potential is highest in June and September which is the two rainfall peak period in Southwest Nigeria.     

深圳市观澜河流域雨水资源可利用潜力评估

雨水资源化利用是解决城镇化进程中城市水问题的重要途径,对其可利用量进行评估是其中重要的步骤。为给深圳市观澜河流域雨水资源利用提供依据,基于深圳市1984—2018年的日降雨资料,采用基于下垫面分类的雨水资源利用潜力计算方法,计算了深圳市观澜河流域在不同典型年的雨水资源量、雨水资源利用理论潜力、现实潜力。结果表明:观澜河流域具有较大的雨水资源利用潜力,其平水年雨水资源利用理论潜力可达3.74亿m³,在70%年径流总量控制率情况下的雨水资源利用现实潜力可达2.42亿m³;在同样的降雨条件下,下垫面类型和城市建设条件均会对雨水资源可利用量产生较大影响,增大园林绿地、水体等下垫面面积和增大年径流总量控制率均有助于提升雨水资源的利用。     

Watershed Modeling to Assessing Impacts of Potential Climate Change on Water Supply Availability

Climate change could have impacts on hydrologic systems threatening, availability of water supply resources. In Illinois, regional water supply planning efforts are attempting to better understand potential impacts on low flow and surface water availability through analysis of hydrologic sensitivity to a range of climate scenarios. This paper explores the development, calibration and validation of Fox River watershed model using the soil and water assessment tool (SWAT) and the model’s application to assess impacts of potential climate change. The watershed model is calibrated and validated using daily flow records at three gauging stations. Automatic model calibration followed by manual refinement of parameter values was performed. Calibration results were generally good for monthly and annual time step but only satisfactory for daily simulations. Based on simulations of global climate models produced for IPCC fourth assessment report, climate scenarios were prepared by the Illinois State Water Survey for water supply planning initiatives in north-east and east-central Illinois. These scenarios showed ranges of temperature change between 0°C to +3.3°C and annual precipitation changes between −127 to +127 mm in the next 50 years, excluding the 5% extreme ends of those climate model simulations considered. Changes in climate were reflected using adjustments to the historical record, instead of using direct outputs from individual climate models. The watershed model was used to assess the impact of potential climate change. Application results indicate that annual precipitation change of 127 mm on average increases annual water yield and 7-day low flows by 28% and 19%, respectively. In contrast, a temperature change of +3.3°C results in average reductions of annual water yield by 13% and 7-day low flows by 10%. Seasonal effects were investigated through evaluation of changes in average monthly flows. Increasing precipitation resulted in significant changes in streamflows in late summer and fall months where as increasing temperature greatly affects winter flows due to snowmelt. The key implication is that climate change-induced variability of streamflows could have major impacts on water supply availability in the Fox River watershed and in particular, increased periods of drought could result in deficit of supplies during seasons of peak water use. It must be noted that this analysis does not examine the potential impacts of population growth and water use on water supply availability, which are also expected to have substantial influences in the region.     

Hydrological Modeling of Zarqa River Basin – Jordan Using the Hydrological Simulation Program – FORTRAN (HSPF) Model

Jordan is an arid country with limited water resources, so there is a chronic need to study and understand its hydrology at the watershed scale which will eventually help in achieving good management for the existing scarce water resources. The studied watershed was the Zarqa River Basin which is considered as the largest watershed in Jordan. The objective of this study was to calibrate the hydrological component of the Hydrological Simulation Program – FORTRAN (HSPF) model for the Zarqa River Basin. The calibrated model could be used in a later stage to examine the impact of different management practices and climate change scenarios on the water resources in the basin. The calibration of the HSPF water quantity parameters was aided by GIS and by the automatic calibration model (PEST). The automatic calibration was done for the years 1988–1991 and the validation was done for the years 1996–1998. The coefficient of determination, R ² for the calibration and verification years of the monthly flows was 0.81 and 0.76, respectively.