Rainwater harvesting systems: An urban flood risk mitigation measure in arid areas

Rainwater harvesting (RWH) systems have been developed to compensate for shortage in the water supply worldwide. Such systems are not very common in arid areas, particularly in the Gulf Region, due to the scarcity of rainfall and their reduced efficiency in covering water demand and reducing water consumption rates. In spite of this, RWH systems have the potential to reduce urban flood risks, particularly in densely populated areas. This study aimed to assess the potential use of RWH systems as urban flood mitigation measures in arid areas. Their utility in the retention of stormwater runoff and the reduction of water depth and extent were evaluated. The study was conducted in a residential area in Bahrain that experienced waterlogging after heavy rainfall events. The water demand patterns of housing units were analyzed, and the daily water balance for RWH tanks was evaluated. The effect of the implementation of RWH systems on the flood volume was evaluated with a two-dimensional hydrodynamic model. Flood simulations were conducted in several rainfall scenarios with different probabilities of occurrence. The results showed significant reductions in the flood depth and flood extent, but these effects were highly dependent on the rainfall intensity of the event. RWH systems are effective flood mitigation measures, particularly in urban arid regions short of proper stormwater control infrastructure, and they enhance the resilience of the built environment to urban floods.

Design Method of Rainwater Harvesting System for Afforestation in Loess Plateau

On the basis of natural conditions of lack of rainfall on the Loess Plateau, this paper presents a method of design and construction in rainwater harvesting system for afforestation, which is suitable to the regions of 300 600?mm rainfall. The system consists of micro catchments of various forms and sizes that include planting areas, where trees are planted and trapped runoff, and contributing areas, where overland flow are produced by rainfall. The design is based on rainfall, runoff coefficients of contributing areas, evapotranspiration of trees and soil surface, water deficiency of soil, and environmental capacity of precipitation in the region, and so on. Runoff coefficient of contributing areas with YJG (organic silicon chemical treatment), compacted surface soil slope and natural slope micro catchments, are 0 8 0 89, 0 23 0 36, and 0 08 0 10 respectively. According to the Penman method, the soil water deficiency varies from 50?mm to 300?mm. In the region of 400?mm precipitation, the contributing area treated with YJG is 3 4?m 2 for timber forests, 8 10?m 2 for cash trees respectively; the contributing area treated with compacted soil surface is 6 8?m\+2 for timber forests, 10 12?m 2 for cash trees respectively; the contributing area of natural slope is 8 10?m 2 for timber forests, 12 15?m 2 for cash trees respectively. Transpiration from trees of micro catchment in YJG, compacted surface soil and natural slope treatment is by 47 65% 53 31%, 24 10% 36 93%, and 18 65% 29 55% of total rainfall (rainfall and harvested rainwater) respectively after the system was applied in the region. This system, which has been widely practising on the Loess Plateau, is now known as runoff forestry.

Design and Construction of Rainwater Harvesting and Water-saving Irrigation System of Toona sinensis on Mountain Slopes

In order to collect rainwater and resist drought to enhance the utilization rate of rainfall and water resources, through project rainwater harvesting measures, the total annual rainwater harvesting amount of the six greenhouses was calculated according to annual average precipitation 542.2 mm, up to 1 095.7 m^3. The upper natural slopes of cultivated land were as rainwater harvesting areas, and total annual rainwater harvesting amount was 49 242 m^3 on the mountain slopes with an area of 73.37 hm^2, while total water storage amount was 39 394 m^3 in theory, so it could meet water use for the irrigation of 26.28 hm^2 of T. sinensis land. To be convenient for rainwater harvesting, irrigation and supplying water to the water-saving cellars, one pert-cut and part-fill reservoir （which was 470 m^3 in volume） was built on the mountain slopes at the right rear of the greenhouses, and their altitude difference was 50 m. The reservoir was sealed and was built with reinforced concrete. Water-saving cellars were distributed in front and the middle and at the back of two rows of greenhouses, and they were connected with each other. The reservoir could supply water to the water-saving cellars and also collect water by mountain slopes, from the lower water-saving cellars or deep wells. Two rainwater hervesting ditches that were 1 650 m in length were at the lower edge of arable land in the upper reaches of slopes to intercept rainfall runoff and make it flow into channels and then the sedimentation tanks. The total annual rainwater harvesting amount of the reservoir and water-saving cellars was 1 222.5 m^3.

A preliminary sustainability assessment of innovative rainwater harvesting for residential properties in the UK

Rainwater harvesting RWH has yet to see significant uptake in UK households primarily due to a lack of innovation in residential RWH system types.This ppa er presents the results of per liminary investigations into a range of traditional and innovative residential-scale RWH systems. These systems are examined using a patent application search informal interviews with industry professionals cost-benefit analysis and a simple multi criteria analysis MCA .The latter examines the sustainability of the systems based on a priori social economic and ne vironmenat l criteria.Two of the innovative systems are subject to a more detailed analysis and benchmarked agains ta rt aditional system.Results of the MCA indicate that the innovative RWH systems achieve better sustainability scores than the traditional RWH with a lower capital cost.Further research is focused on monitoring the identified systems to generate empir cal datasets in order to undertake the WLC/LCAs and to identify challenges associated with installation.

Water and Energy Conservation of Rainwater Harvesting System in the Loess Plateau of China

Water is the source of all the creatures on the earth and energy is the main factor driving the world. With the increasing population and global change, water and energy conservation have become worldwide focal issues, particularly in the water-stressed and energy-limited regions. Rainwater harvesting, based on the collection and storage of rainfall runoff, has been widely used for domestic use and agricultural production in arid and semiarid regions. It has advantages of simple operation, high adaption, low cost and less energy consumption. This study reviewed rainwater harvesting systems adopted in the Loess Plateau of China and analyzed water use efficiency （WUE） for various rainwater harvesting techniques. Supplemental irrigation using harvested rainwater could increase crop yield by more than 30%, and WUE ranged from 0.7 to 5.7 kg m4 for spring wheat, corn and flax, and 30-40 kg m-3 for vegetables. Moreover, energy consumption for rainwater harvesting based on single family was compared with traditional water supply in the city of the Loess Plateau using the life cycle assessment （LCA） method. Results showed that energy consumption yielded per unit harvested rainwater was 25.96 MJ m-3 yr which was much less than 62.25 MJ m3 yr^-1 for main water supply in Baoji City, Shanxi Province, meaning that rainwater harvesting saved energy by 139.8% as compared to the main water supply system. This study highlights the importance and potential of rainwater harvesting for water and energy conservation in the near future.

Rainwater harvesting to alleviate water scarcity in dry conditions:A case study in Faria Catchment,Palestine

In arid and semi-arid regions, the availability of adequate water of appropriate quality has become a limiting factor for development. This paper aims to evaluate the potential for rainwater harvesting in the arid to semi-arid Faria Catchment, in the West Bank, Palestine. Under current conditions, the supply-demand gap is increasing due to the increasing water demands of a growing population with hydrologically limited and uncertain supplies. By 2015, the gap is estimated to reach 4.5 x 106 m3. This study used the process-oriented and physically-based TRAIN-ZIN model to evaluate two different rainwater harvesting techniques during two rainfall events. The analysis shows that there is a theoretical potential for harvesting an additional 4 x 106 m3 of surface water over the entire catchment. Thus, it is essential to manage the potential available surface water supplies in the catchment to save water for dry periods when the supply-demand gap is comparatively high. Then a valuable contribution to bridging the supply-demand gap can be made.

Ridge-furrow rainwater harvesting with supplemental irrigation to improve seed yield and water use efficiency of winter oilseed rape(Brassica napus L.)

Ridge-furrow rainwater harvesting （RFRH） planting pattern can lessen the effect of water deficits throughout all crop growth stages, but water shortage would remain unavoidable during some stages of crop growth in arid and semiarid areas. Supplemental irrigation would still be needed to achieve a higher production. Field experiments were conducted for two growing seasons （2012-2013 and 2013-2014）to determine an appropriate amount of supplemental irrigation to be applied to winter oilseed rape at the stem-elongation stage with RFRH planting pattern. Four treatments, including supplemental irrigation amount of 0 （I1）, 60 mm （I2） and 120 mm （I3） with RFRH planting pattern and a control （CK） irrigated with 120 mm with flat planting pattern, were set up to evaluate the effects of supplemental irrigation on aboveground dry matter （ADM）, nitrogen nutrition index （NNI）, radiation use efficiency （RUE）, water use efficiency （WUE）, and seed yield and oil content of the oilseed rape. Results showed that supplemental irrigation improved NNI, RUE, seed yield and oil content, and WUE. However, the NNI, RUE, seed yield and oil content, and WUE did not increase significantly or even showed a downward trend with excessive irrigation. Seed yield was the highest in 13 for both growing seasons. Seed yield and WUE in 13 averaged 3235 kg ha^-1 and 8.85 kg ha^-1 mm-1, respectively. The highest WUE was occurred in 12 for both growing seasons. Seed yield and WUE in 12 averaged 3089 kg ha^-1 and 9.63 kg ha^-1 mm^-1, respectively. Compared to 13, 12 used 60 mm less irrigation amount, had an 8.9% higher WUE, but only 4.5 and 0.4% lower seed yield and oil content, respectively. 12 saved water without substantially sacrificing yield or oil content, so it is recommended as an appropriate cultivation and irrigation schedule for winter oilseed rape at the stem-elongation stage.

Rainwater harvesting in the challenge of droughts and climate change in semi-arid Brazil

Some successful experiences of rainwater harvesting in Brazil’s semi-arid region are shown how rural communities are living during the severe drought from 2011 to 2013 using technologies of rainwater harvesting for the household in agriculture livestock raising and the environment.Starting from the positive experiences principles of living in the challenge of droughts and climate change are elaborated and summarized into different guidelines for sustainable livelihood and production access to water and sufficient land area rainwater harvesting to provide water security to households and communities preservation recovering and management of drought-resistant vegetation emphases on raising of small and medium sized livestock and water and forage storage appropriate crop selection and sustainable extraction processing and marketing of crop products capacity building of the people. These principles contribute to preparing a national policy on living in harmony with the semi-arid climate. Rainwater harvesting is an important part of a package of measures which enables a sustainable livelihood in such a difficult environment.

Household model of rainwater harvesting system in Mexican urban zones

This paper describes a household model of the rainwater harvesting system in residential development of Tlaquepaque Jalisco Mexico. Harvested rainwater is estimated for designing a rainwater catchment system which reflects the maximum water supply to a household.Based on the estimation of the harvested rainwater the total water demand is calculated in order to explore the possible uses of rainwater. Major components in the rainwater catchment system are as follows catchment area downspout roof drain pipe and first flush tank cistern infiltration well pumping station and filtering system and ultraviolet UV water treatment.The rainwater harvesting system is designed to operate as the part of the central water supply system.This paper exposes the process of design and construction and its cost.In this way it aims to establish a technical and conceptual reference which enables the citizens to design their rainwater systems and their construction. This model will produce an important experience that can help to improve the systems in a Mexican context.It can be also useful for the international community.

Impact Assessment of Hillside Rainwater Harvesting Ponds on Agriculture Income: Case Study of Ntarama Sector in Rwanda

Nowadays, rainwater harvesting (RWH) technology is increasingly adopted as a strategic pathway for reducing poverty in rural drought prone areas for enhancing agricultural productivity and boosting farm income. The aim of this study is to assess the level of adoption and the impacts of RWH ponds on farm income in Ntarama sector of Bugesera District in Eastern Province of Rwanda. Fifteen farm ponds were visited and the level at which households adopted RWH ponds, their impact on farm income and performance in storing water were assessed. Interviews and questionnaires methods were used to farm ponds beneficiaries and the storage capacity of farm ponds was calculated to ensure that they meet irrigation water demand. Then, Microsoft excel was used as a data analysis tool. The results show that 42.5% of households have adopted RWH ponds and the adoption level of RWH ponds fails due to the lack of training about the role and use of RWH ponds before their implementation. Beside this the low level of public involvement during the site selection for ponds associated with social conflicts among water users was observed. However, it is further revealed that the use of RWH ponds positively impacts on agricultural income on 1/4 hectare per year by about 2,325,000 RWF (3100USD). The studied portion of area can bear 222 ponds of 120 m3 each if all the rain is harvested throughout the year instead of being three ponds. Furthermore, we found that the quantity of rainwater harvested of 328.5 m3 as a total of the 3 ponds was still too less to meet irrigation water demand. As negative impacts, the RWH technology can cause dangerous effects such as social conflicts, breeding site for mosquitoes, water related diseases, accidents and others with a level of severity of 32%, 24%, 20%, 16% and 8%, respectively. This happens when the RWH ponds are not properly managed.

Rooftop Rainwater Harvesting as an Alternative Domestic Water Resource in Zambia

Within the last decade, substantial progress has been achieved in the management of centralized water reticulation in Zambia. Characterized by diversified fiscal resourcing, concurrent institutional restructuring and introduction of new players in water governance, the water sector is set to achieve improved reliability on sustainable grounds. However, the threat of underground water pollution resulting from increased urbanization besides the unreliable energy sector presents new challenges for the current urban water. In effect, urban areas are affected by chronic water rationing creating public stress and insecurity which impacts domestic development. While the course of development has meant investment in the extension and expansion of water infrastructure in Zambia, alternative urban water resources are being sought to address challenges of traditional water systems globally. This paper therefore attempts to make a case for the modernization of Rooftop Rainwater Harvesting (RRWH) as an augmenting water resource in the Zambian urban housing sector. Here—in, it is identified as a Low Impact Development technology within the Integrated Urban Water Management framework currently being forged by local water. Based on a desktop literature survey and online questionnaire survey, an argument to support the development of RRWH in Zambia was developed. While literature survey results revealed evidence of economic loss and a growing compromise to public health resulting from inconsistent water supply in the study area of Lusaka city, the online questionnaire survey depicted significant domestic stress due to erratic water supply. Results confirmed that at one time residents observed an average of eight hours of power blackouts which effectively induced water disruption forcing homeowners to engage in various water storage methods which in turn are costly on domestic time, health and finances. A retrospective discussion based on both survey results attempts to present benefits and opportunities of urban RRWH to water sector stakeholders providing recommendations towards the mainstreaming of the practice in Zambia.

Efficiency and Economy of a New Agricultural Rainwater Harvesting System

Shortage of water is the key limiting factor for agricultural development of Beijing.Rainwater harvesting(RWH) could provide an alternative water source for greenhouse agriculture,but local natural and socioeconomic conditions challenge the application of the technology.This article analyses the advantages and disadvantages of different types of greenhouse RWH in Beijing,and describes a new greenhouse RWH system demonstrated in 2008 in Huairou,a suburb district of Beijing.It analyses the efficiency,cost-benefit ratios and limiting factors of the new system.The results show that with the new system,RWH efficiency can be as high as 66%(of total rainfall) and the rainwater usage rate can reach 69% of total water usage.The ratio of benefit to cost of government investment can be 1.84,and the ratio of benefit to cost of a farmer's investment could be 1.68 provided the project is designed to save water and also increase income.However,the price of groundwater for agriculture directly influences the potential for applying and scaling up the project.If the RWH system does not increase the farmers' incomes at the current water price,they will not use it until the water price rises to a critical point,which is determined by external factors.This article also suggests a number of measures to increase the efficiency of the system in order to apply it on a large scale.

Water harvesting experiences from the southern and eastern Africa rainwater network

This paper shares experiences of the southern and eastern Africa rainwater network on rainwater harvesting.It also shares the lessons drawn from policy research awareness creation and networking building of national networks and assessment of promising water harvesting techniques in the Sub-Saharan Africa.The concerted promotional effort of the southern and eastern Africa rainwater network has resulted in the general acceptance of rainwater harvesting as a viable option for boosting domestic water supply agricultural production and environmental sustainability.To date twelve nationally registered rainwater harvesting associations have been established which are providing leadership and capacity building in rainwater harvesting.Governments and donors are also aligning their policies towards providing increased financial institutional and technical support for upscaling rainwater-harvesting techniques. This paper concludes that diligent land and water management is necessary for yielding the highest benefits from rainwater.In addition to enabling policies and institutions there must be ample budgetary support to increase adoption of the technology.

Introduction to rainwater management in Australia and suggestions for China's water problems

Australia is one of the world leaders in water management. The country meets the challenge of water shortage with established integrated water management in which rainwater is taken as a too precious resource to be just drained off. In Australia, rainwater is extensively harvested and polished to provide cheaper supply for potable and non-potable domestic uses, irrigation, landscaping, refilling aquifers and other uses. Implementing dual management over the quantity and quality of storm water and practicing water sensitive urban design (WSUD) in urban areas effectively control non-point-source pollution of waterways by pollutants carried with runoffs, reduce the discharge of rainwater and thus protect properties and lives from damage by floods. These achievements are attributed to constant reinforcement by govenments from federal to local levels in policy, financial, legal and educational aspects, and also to the lasting efforts of professional communities and water industry in developing requisite techniques, demonstrating the benefits and fostering public credence of rainwater reuse. The successful rainwater management practices in Australia suggest rainwater harvesting can be a complimentary means for the South-to-North Water Transfer Scheme to solve the water shortage in China's northern regions, and thus release to a degree the pressure on the Yangtze water resources. Best management practices of rainwater can be an effective controlling strategy for flooding and non-point-source water pollution of waterways. Such in-site source control initiatives have particular significance to protecting slow waterways of weak self-purification ability, like the Three Gorges Reservior.

Sustainable Water Supply for Domestic Use： Application of Roof-Harvested Water for Ground Water Recharge

Rain water harvesting offers a wealth of promising possibilities for many countries. This paper describes a study in which rainwater harvested from the rooftop is used for recharging groundwater in a household well in Ibadan. A rainwater harvesting structure was designed to be 1.2 m deep, 2.6 m long and 0.66 m wide, filled with gravel and fine sand at different layers. Rainwater harvested in a storage tank is passed with the aid of a hose pipe to the rainwater harvesting structure on a daily basis to recharge the groundwater in the well. A well in the neighborhood serves as control for this experiment, which went on for a month. The volume of rainwater used to recharge the groundwater in the well was recorded daily for the study period. The results indicated that using rainwater to recharge the groundwater in the well led to conservation of the water in the well through reduced evaporation. Thus, the well yields water all the year round as compared to the control well that dries up during the dry season.

Potential of rooftop rainwater harvesting to meet outdoor water demand in arid regions

The feasibility of rooftop rainwater harvesting （RRWH） as an alternative source of water to meet the outdoor water demand in nine states of the U.S. was evaluated using a system dynamics model developed in Systems Thinking, Experimental Learning Laboratory with Animation. The state of Arizona was selected to evaluate the effects of the selected model parameters on the efficacy of RRWH since among the nine states the arid region of Arizona showed the least potential of meeting the outdoor water demand with rain harvested water. The analyses were conducted on a monthly basis across a 10-year projected period from 2015 to 2024. The results showed that RRWH as a potential source of water was highly sensitive to certain model parameters such as the outdoor water demand, the use of desert landscaping, and the percentage of existing houses with RRWH. A significant difference （as high as 37.5%） in rainwater potential was observed between the projected wet and dry climate conditions in Arizona. The analysis of the dynamics of the storage tanks suggested that a 1.0-2.0 m3 rainwater barrel, on an average, can store approximately 80% of the monthly rainwater generated from the rooftops in Arizona, even across the high seasonal variation. This interactive model can be used as a quick estimator of the amount of water that could be generated, stored, and utilized through RRWH systems in the U.S. under different climate conditions. The findings of such comprehensive analyses may help regional policymakers, especially in arid regions, to develop a sustainable water management infrastructure.

Rainwater Harvesting in Multifamily Social Interest Housing

This study evaluated the reduction of water consumption in a SIH （social interest housing） complex from the simulation of implanting a rainwater harvesting system. The methodology consisted of characterization of the case study, survey data of water consumption and data of precipitation in the area, on-site visits to define the average consumption and monthly water distribution, and sizing of a rainwater harvesting tank following the Netuno Program. It was obtained 22.500 L as the ideal volume for the tank, supplying the demand for drinkingwater in 32%, although the reduction in the drinking water bills would be minor, since the object of the case study is considered SIH, and residents pay a fixed fee for consuming up to 10 m3 per month. Therefore, it becomes necessary to analyze this situation from a sustainable and environmental perspective, and the benefits are no longer only economic, but rather they take on a more comprehensive social dimension.

Strategy to Overcome Barriers of Rainwater Harvesting, Case Study Tanzania

There are socio-technological challenges towards extension of the application of rainwater harvesting (RWH) practices in developing countries. An attempt to address this was done using the Mnyundo Primary School, Tanzania, as a study area for evaluating the technical, economic, and social challenges of RWH practices. A storage water level monitoring gauge was used so as to simplify rainwater quantity control and utilization strategy. Basic quality control components such as first flush tank were incorporated so as to reduce the particle load flowing into the storage. Cost reduction strategies such as the one (1) company one (1) community campaign were applied to address the cost implication. To enhance ownership, participatory approach of the beneficiaries in all stages including planning, designing and implementation was adopted. In order to ensure project sustainability, training on how to operate and maintain were provided as well as a maintenance manual to impart a sense of ownership. For the challenges of imparting RWH practices in Tanzania, 19 solutions have been identified and they include provision of RWH manuals, guidelines and regulations, government incentives, and promotion of self-financing initiatives. For developing countries, the study proposes the following strategies: establishing relevant regulations and research centers, enhancing individual and community financial stability, conducting demonstration projects, and increased investment by government on promotion.

Strategies for Household Water Supply Improvement with Rainwater Harvesting

There are significant household water supply challenges including quantity sufficiency and quality, which have economic and social implications. The challenges have remained despite the efforts of government establishing centralized or groundwater systems, and/or having individual crude systems. A Tanzanian rural household case study was considered by assessing the performance of a currently relied surface runoff collecting pond system for domestic purposes. A daily water balance model was applied with performance parameters, no water days (NWD) and rainwater usage (RUR). Rooftop runoff harvesting system was proposed as a water supply source in addition to the current one. Under such dual supply conditions, users can meet the drinking and non-drinking demand even in dry seasons at a minimum of 2 and 20 L/person/d, respectively. For rainwater harvesting adoption (considering selected regions), it was further established that amount and variation in rainfall impacts on quantity available for meeting demand. Increased catchment implies increased harvestable quantity, and with same storage higher reduction of number of NWD although with slight decrease of RUR. Also, increased storage is required for achieving higher RUR in case the same demand is maintained. But same storage can be maintained for increased demand relative to catchment size. However, rainwater catchment increase has greater impact on meeting a specified demand under given condition of rainfall quantity and variation. The RWH technology strategies presented in this study are replicable in other developing countries under site specific conditions.

Socio-Economic and Environmental Impacts Assessment of Using Different Rainwater Harvesting Techniques in Sarida Catchment, West Bank, Palestine

A statistically representative questionnaire targeted people using rainwater harvesting(RWH)techniques in rural communities of Sarida catchment,West Bank,Palestine was distributed and analyzed.The main objective of this study is to assess the social,economic,and environmental impacts of adopting RWH techniques(e.g.cisterns,concrete and clay ponds,Wadi ponds,earth dams,and stone terraces)in different uses to increase water availability.The results showed a simple sharing of the female component among beneficiaries,while concrete ponds and cisterns were the most used techniques.Actually,social impacts were noticeable by sharing the same RWH structure and reflected to responsibility skills and role exchange increases.On the other hand,RWH techniques showed a significant economic impact for end users represented by enhancing domestic,agricultural,and recreational activities leading to good profit increase.In addition to food security as output,the most important environmental impact was water wasting prevention,which in turn could be linked to sustainable water management and considered as universal challenge for future generations.