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.

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.

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.

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.

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.

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.

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.

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.

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.

Analysis of a rainwater harvesting system for domestic water supply in Zhoushan,China

The domestic rainwater harvesting system (DRHS) is an important freshwater source for Zhoushan,China to meet water demands. A computer model has been generated to analyze the performance of the DRHS with different ratios of D/(AR) (water demand/average annual collected runoff) and S/(AR) (storage capacity/average annual collected runoff). The performance of the DRHS was analyzed by means of the model simulation,which is described by its water shortage rate (WSR) and water loss rate (WLR). Using the data,a set of dimensionless design calculation chart is introduced. When the water demand and requirement of the design are known,the established chart can be used to easily determine the storage capacity and catchment (roof and other surface) area required to achieve a desired performance level.

Rainwater harvesting,its prospects and challenges in the uplands of Talugtog,Nueva Ecija,Philippines

The prospects and challenges facing eight small water impounding projects(SWIPs)in Talugtog,Nueva Ecija,an upland municipality located in Central Luzon,Philippines were evaluated using rapid appraisal and documentation of projects,interview of farmers and local officials,and a review of related studies undertaken on the same project sites.The challenges include the deterioration of structural facilities,inactive farmers associations,watershed degradation,and climate change.It also aims to evaluate improvement and innovation in the future implementation of SWIPs as rainwater harvesting facilities.The site was selected because it has the largest number of SWIPs established as one of the coping strategies during the 1997-1998 severe El Nino.Because of its location,it has no major irrigation systems and relies only on local rainwater storage facilities.The study involves 8 SWIPs established in two clusters(i.e.,5 and 3 SWIPs in a watershed)as rainwater conservation and management facilities.Results indicated these clusters of SWIPs offer multiple benefits in terms of supplemental irrigation,inland fish production,and water for domestic purposes and livestock production.They also serve as strategic small-scale upland structures that enhance recharging of groundwater,prevent flooding,and provide value-adding activities such as recreation,soil and water conservation,and environmental benefits.Previous studies also identified their benefits at the farm and community levels as conserved rainwater through storage in SWIPs is translated into more economic uses.However,some SWIPs are confronted with various challenges;deterioration of structural facilities,inactive farmer associations,unabated watershed degradation,and threats of climate change.These are seriously affecting the overall performance of SWIPs.Immediate actions should include the strengthening of small water impounding system associations(SWISA),repair and climate-proofing of structural facilities through the(SWISA)themselves,and watershed protection and management through the adoption of appropriate soil and water conservation measures.

Improving water use efficiency by integrating fish culture and irrigation in coconut based farming system:A case study in Kasaragod District of Kerala(India)

The crop production in the district of Kasaragod in Kerala State(India)is characterized by low input-low yield concept and rain-fed agriculture.A field study was conducted in Western Ghat region of the district to develop a suitable rainwater harvesting system adoptable to hilly terrains and to test its efficacy for improving the use efficiency of the harvested water by its multiple uses.The cost-benefit analysis of the water harvesting system was also carried out to find out its affordability to farmers.The water harvesting system has been developed by integrating three components:(i)improving the productivity of coconut and component crops in the cropping units(ii)developing multiple water use systems,and(iii)the conjunctive use of the harvested water along with other surface and groundwater resources.Based on the estimated annual costs and returns,the Benefit-Cost ratio was found to be 1.69 and all other financial viability criteria(IRR and NPV)were also found favourable for investment on a lined water harvesting tank integrated with a micro-irrigation system and fish farming.The study suggested that the rainwater harvesting could be implemented as a viable alternative to conventional water supply or on-farm irrigation projects considering the fact that any land anywhere can be used to harvest rainwater.Further,the water use efficiency can be improved through effective harvesting and subsequent multiple uses of stored water.

Life cycle assessment of low impact development technologies combined with conventional centralized water systems for the City of Atlanta, Georgia

Low-impact development （LID） technologies, such as bioretention areas, rooftop rainwater harvesting, a_nd xeris_caping can co_ntrol stormwater runoff, supply non-potable water, and landscape open space.TillS study examines a hybrid system （HS） that combines LID technologies with a centralized water system to lessen the burden on a conventional system （CS）. CS is defined as the stormwater collection and water supply infrastructure, and the conventional landscaping choices in the City of Atlanta. The study scope is limited to five single-family residential zones （SFZs）, classified R-1 through R-5, and four multi-family residential zones （MFZs）, classified RG-2 through RG-5. Population density increases from 0.4 （R-1） to 62.2 （RG-5） persons per 1,000 m2. We performed a life cycle assessment （LCA） comparison of CS and HS using TRACI 2.1 to simulate impacts on the ecosystem, human health, and natural resources. We quantified the impact of freshwater consumption using the freshwater ecosystem impact （FEI） indicator. Test results indicate that HS has a higher LCA single score than CS in zones with a low population density; however, the difference becomes negligible as population density increases. Incorporating LID in SFZs and MFZs can reduce potable water use by an average of 50%. and 25%,respectively.; however, water savings are negligible in zones with high population density （i.e., RG-5） due to the diminished surface area per capitaavailable for LID technoogies. The results demonstrate that LID technologies effectively reduce outdoor water demand and therefore would be a good choice to decrease the water consumption impact in the City of Atlanta.

Making rainfed agriculture sustainable through environmental friendly technologies in Pakistan:A review

Pakistan is an agricultural country spreading over an area of about 79.6 million hectares(Mha)with an arid and semi arid climate.Of 79.6 Mha,about 23 Mha is suitable for crop production and nearly 25 percent of the total cultivated area is designated for rainfed agriculture.Unfortunately,rain-fed agriculture is constrained with multifarious problems such as moisture stress,soil erosion and crusting,nutrient deficiency,depletion and poor nutrient use efficiency,and weed infestation limiting the yield potential of these lands.In addition,deforestation and poor crop husbandry techniques are commonly noticed features.To meet the food requirements,farmers bring all the available pieces of lands under plough including steep slopes.Farming on steep slopes if not managed on scientific lines,results in severe erosion.The problems faced by the farmers are due to the unsustainable practices they adopt to practice dryland agriculture,limiting the productive potential of these important ecosystems.However,their potential can be improved by adopting suitable rainwater harvesting techniques;employing scientific soil and water conservation methods and using sustainable agricultural practices.This paper highlights some important issues associated with the rainfed agriculture of Pakistan.Working strategies for realizing optimum and sustainable yields have been outlined while conserving both land and water resources.

Pollutant reduction effectiveness of low-impact development drainage system in a campus

Building a rainwater system based on the idea of low-impact development （LID） is an important aspect of the current ＂sponge city＂ construction in China. The ＂sponge city＂ concept emphasizes that the runoff can permeate the soil or be stored temporarily, and rainwater could be used again when it is needed. Beijing is one of the earliest cities to study rainwater harvesting and LID techniques in China.Through long-terua monitoring of rainfall, runoff flow, and water quality of a campus demonstration project in Beijing, the runoff quantity and pollutant concentration variations have been analyzed. Furthermore, the runoffreduction effects of single LID measure, such as green roof, filtration chamber, and permeable pavement, have been investigated. Additionally, the overall reduction effectiveness of the LID system on the average annual rainfall runoff and pollution load has been discussed.