Showing papers on "Rainwater harvesting published in 2009"

Evolving Urban Water and Residuals Management Paradigms: Water Reclamation and Reuse, Decentralization, and Resource Recovery

Abstract: Population growth and improving standards of living, coupled with dramatically increased urbanization, are placing increased pressures on available water resources, necessitating new approaches to urban water management The tradition linear "take, make, waste" approach to managing water increasingly is proving to be unsustainable, as it is leading to water stress (insufficient water supplies), unsustainable resource (energy and chemicals) consumption, the dispersion of nutrients into the aquatic environment (especially phosphorus), and financially unstable utilities Different approaches are needed to achieve economic, environmental, and social sustainability Fortunately, a toolkit consisting of stormwater management/rainwater harvesting, water conservation, water reclamation and reuse, energy management, nutrient recovery, and source separation is available to allow more closed-loop urban water and resource management systems to be developed and implemented Water conservation and water reclamation and reuse (multiple uses) are becoming commonplace in numerous water-short locations Decentralization, enabled by new, high-performance treatment technologies and distributed stormwater management/rainwater harvesting, is furthering this transition Likewise, traditional approaches to residuals management are evolving, as higher levels of energy recovery are desired, and nutrient recovery and reuse is to be enhanced A variety of factors affect selection of the optimum approach for a particular urban area, including local hydrology, available water supplies, water demands, local energy and nutrient-management situations, existing infrastructure, and utility governance structure A proper approach to economic analysis is critical to determine the most sustainable solutions Stove piping (ie, separate management of drinking, storm, and waste water) within the urban water and resource management profession must be eliminated Adoption of these new approaches to urban water and resource management can lead to more sustainable solutions, defined as financially stable, using locally sustainable water supplies, energy-neutral, providing responsible nutrient management, and with access to clean water and appropriate sanitation for all

SCS-CN and GIS-based approach for identifying potential water harvesting sites in the Kali Watershed, Mahi River Basin, India

Abstract: The Kali sub-watershed is situated in the semi-arid region of Gujarat, India and forms a part of the Mahi River Watershed. This watershed receives an average annual rainfall of 900mm mainly between July and September. Due to high runoff potential, evapo-transpiration and poor infiltration, drought like situation prevails in this area from December to June almost every year. In this paper, augmentation of water resource is proposed by construction of runoff harvesting structures like check dam, percolation pond, farm pond, well and subsurface dyke. The site suitability for different water harvesting structures is determined by considering spatially varying parameters like runoff potential, slope, fracture pattern and micro-watershed area. GIS is utilised as a tool to store, analyse and integrate spatial and attribute information pertaining to runoff, slope, drainage and fracture. The runoff derived by SCS-CN method is a function of runoff potential which can be expressed in terms of runoff coefficient (ratio between the runoff and rainfall) which can be classified into three classes, viz., high (>40%), moderate (20–40%) and low (<20%). In addition to IMSD, FAO specifications for water harvesting/recharging structures, parameters such as effective storage, rock mass permeability are herein considered to augment effective storage. Using the overlay and decision tree concepts in GIS, potential water harvesting sites are identified. The derived sites are field investigated for suitability and implementation. In all, the accuracy of the site selection at implementation level varies from 80–100%.

Global potential to increase crop production through water management in rainfed agriculture

Abstract: This modeling study explores—spatially explicitly, for current and projected future climate, and for different management intensity levels—the potential for increasing global crop production through on-farm water management strategies: (a) reducing soil evaporation (‘vapor shift’) and (b) collecting runoff on cropland and using it during dry spells (‘runoff harvesting’). A moderate scenario, implying both a 25% reduction in evaporation and a 25% collection of runoff, suggests that global crop production can be increased by 19%, which is comparable with the effect of current irrigation (17%). Climate change alone (three climate models, SRES A2r emissions and population, constant land use) will reduce global crop production by 9% by 2050, which could be buffered by a vapor shift level of 50% or a water harvesting level of 25%. Even if realization of the beneficial effects of rising atmospheric CO2 concentration upon plants was ensured (by fertilizer use) in tandem with the above moderate water management scenario, the water available on current cropland will not meet the requirements of a world population of 9–10 billion.

Storm Water Runoff Mitigation Using a Green Roof

Abstract: A prototype green roof was constructed and monitored in Pittsburgh, Pennsylvania, to demonstrate a way to reduce storm water runoff and combined sewer overflow (CSO) events. The large impervious surface area created by urban development in Pittsburgh creates a wet weather flow that the existing combined waste waster and storm water sewer system cannot contend with. Green or vegetated roofs can reduce the amount of storm water that reaches the sewer conveyance system by replacing an otherwise impervious roof with porous soil that retains rainwater and plants that evapotranspire resulting in reduced storm water flows to the sewer system. The prototype green roof reduced the runoff volume by up to 70% compared to a conventionally ballasted roof covering a control portion of the same building. A reduction of at least 20% was found for rainfalls of 1.5 cm (0.60 inches) or less. The green roof also reduced the flow rate of runoff throughout storms. Peak values from the green roof were between 5% and 70% lower t...

Rainfed Agriculture: Unlocking the Potential

Abstract: 1. Rainfed Agriculture - Past Trends and Future Prospects 2. Zooming in on the Global Hotspots of Rainfed Agriculture in Water Constrained Environments 3. Water Resource Implications of Upgrading Rainfed Agriculture - Focus on Green and Blue Water Trade-offs 4. Tectonics-climate Linked Natural Soil Degradation and its Impact in Rainfed Agriculture: Indian Experience 5. Determinants of Crop Growth and Yield in a Changing Climate 6. Yield Gap Analysis: Modeling of Achievable Yields at Farm Level 7. Can Rainfed Agriculture Feed the World? - An Assessment of Potentials and Risk 8. Opportunities for Improving Crop-water Productivity Through Genetic Enhancement of Dryland Crops 9. Water Harvesting for Improved Rainfed Agriculture in the Dry Environments 10. Supplemental Irrigation for Improved Rainfed Agriculture: In WANA Region 11. Opportunities for Water Harvesting and Supplemental Irrigation for Improving Rainfed Agriculture in Semi-arid Areas 12. Integrated Farm Management Practices and Up Scaling the Impact for Increased Productivity of Rainfed Systems 13. Challenges of Adoption and Adaptation of Land and Water Management Options in Smallholder Agriculture: Synthesis of Lessons and Experiences 14. Scaling-out Community Watershed Management for Multiple Benefits in Rainfed Areas.

Assessment of rainwater quality from rainwater harvesting systems in Ontario, Canada

Abstract: Rainwater samples were collected from rainwater harvesting (RWH) systems at seven sites located in a 30 km radius around the City of Guelph in Ontario, Canada. From October 2006 to October 2007, a total of 360 samples were collected from two sampling locations—the rainwater cistern and at the point of use—and analysed for pH, turbidity, colour, total and fecal coliforms, total organic carbon, total nitrogen and UV absorbance (254 nm). Additional parameters, including polycyclic aromatic hydrocarbons, total metals, Campylobacter and Legionella were examined in selected samples. Following data collection, statistical analysis was performed to investigate the factors that influenced rainwater quality. The results of the quality assessment programme were largely consistent with those reported by several other researchers, with the exception of improved microbiological quality during periods of cold weather. Total and fecal coliforms were detected in 31% and 13% of the rainwater samples, respectively, while neither Campylobacter nor Legionella were detected above 1 CFU/100 ml detection limits. The results indicate that, while quality can be expected to vary with environmental conditions, the rainwater from a RWH system can be of consistently high quality through the selection of appropriate catchment and storage materials and the application of post-cistern treatment.

Rainwater harvesting as an alternative water resource in rural sites in central northern Namibia

Abstract: In this paper, results of the investigations on rainwater harvesting (RWH) in central northern Namibia are described, which are part of the transdisciplinary research project CuveWaters. On the basis of hydrological and technical as well as social and cultural conditions, appropriate solutions for RWH are developed, discussed, and evaluated. The main objective is to analyse their technical and economical feasibility as well as their affordability for future users. In detail, two small-scale RWH systems are examined: roof catchments using corrugated iron roofs as rain collection areas and ground catchments using treated ground surfaces. The current status of local water supply and water use was investigated in the village of Epyeshona. Concepts and techniques of RWH were discussed with the population. Based on the results of these investigations and on the physical conditions, the appropriate RWH design and the required storage capacities could be identified. Local material and labour costs were determined and a dynamic cost analysis was carried out to compare the technological options in terms of amortisation times and prime costs. The feasibility of the RWH systems was assessed in relation to local socio-economic conditions. The calculations reveal that it is economically feasible to apply decentral techniques of RWH in terms of the roof catchment systems. Moreover, the proposed technologies provide comparable benefits to the public water supply. The ground catchment system, however, needs moderate subsidies to obtain the same benchmark.

Understanding the physical processes of pollutant build-up and wash-off on roof surfaces

Abstract: Pollutants originating with roof runoff can have a significant impact to urban stormwater quality. This signifies the importance of understanding pollutant processes on roof surfaces. Additionally, knowledge of pollutant processes on roof surfaces is important as roofs are used as the primary catchment surface for domestic rainwater harvesting. In recent years, rainwater harvesting has become one of the primary sustainable water management techniques to counteract the growing demand for potable water. Similar to all impervious services, pollutants associated with roof runoff undergo two primary processes: build-up and wash-off. The knowledge relating to these processes is limited. This paper presents outcomes of an in-depth research study into pollutant build-up and wash-off for roof surfaces. The knowledge will be important in order to develop appropriate strategies to safeguard rainwater users from possible health risks.

Rainwater harvesting in petrol stations in Brasília: Potential for potable water savings and investment feasibility analysis

Abstract: Rainwater harvesting is an important way of optimizing the usage of water resources and promoting sustainable development. The objective of this article is to evaluate the potential for potable water savings by using rainwater for washing vehicles in petrol stations located in Brasilia, Brazil. An investment feasibility analysis was also performed. The study was carried out by using Neptune, a computer programme for rainwater harvesting analysis. Rainfall data from two meteorological stations were considered, as well as different rainwater collecting areas, tank capacities, number of washings, and potable and rainwater demands. As for the rainwater demands, they were considered as a percentage of the potable water demand, varying according to the day of the week. The tank capacities were varied at increments of 1000 L. The investment feasibility analysis was performed for three different cases, taking into account the potential for potable water savings. It was observed that the average potential for potable water savings by using rainwater is 32.7%, but it can vary from 9.2% to 57.2%. The main conclusion obtained from this work is that using rainwater for washing vehicles in petrol stations in Brasilia is a feasible investment for most cases as the net present value is positive for an interest rate of 1% per month.

Water Balance Approach for Rainwater Harvesting using Remote Sensing and GIS Techniques, Jammu Himalaya, India

Abstract: Judicious use of the limited fresh water resources is the need of the hour. If sufficient measures are not taken up immediately, we will face a crisis which will be detrimental to the very survival of mankind. The Kandi region of Jammu district in Jammu Himalaya is facing a similar problem of acute shortage of drinking water. One of the most logical steps towards this goal would be acknowledging the importance of rainwater harvesting. The Central Ground Water Board (CGWB), North Western Himalayan Region, Jammu, has already initiated few schemes to recharge and conserve the water resources. The water resources in this study area have been estimated by water balance assessment approach. The water balance study using the Thornthwaite and Mather (TM) models with the help of remote sensing and GIS is very helpful in finding out the moisture deficit and moisture surplus for an entire watershed. The water balance calculation shows that the maximum annual runoff results from the built-up areas/water body followed by agricultural land, dense forest and minimum for the barren land and open forest. The annual deficit in the Devak–Rui watershed is 0.38 mm and the annual surplus is 1,251.34 mm. GIS software’s have been used for spatial analysis for generation of various thematic layers and integration to produce the final runoff map. The total runoff of Devak–Rui watershed was calculated as 1,160.48 mm from the total precipitation of 1,429.26 mm. It was found that suitable sites for rainwater harvesting structures in the Devak–Rui watershed covers an area of nearly 11% of the watershed area whereas the rest of the watershed area was assumed as unsuitable site for rainwater harvesting.

Rainwater harvesting : a lifeline for human well-being.

Abstract: ion for water supply. Rainwater harvesting can be used to improve ecosystem function, particularly the water supply aspect, and regulation (controlling flood and erosion). Globally, there is a significant untapped potential in rainwater which can be harvested to improve ecosystem services and human well-being. This chapter addresses the contribution of rainwater in improving ecosystem services related to rural and urban water supplies. 6.2 RAINWATER HARVESTING, ECOSYSTEMS AND RURAL WATER SUPPLY Most people living in rural areas depend on development which is based on ecosystem services. Typical rural ecosystem services that support human livelihoods include water supply, agriculture including livestock management, fisheries, and forest and tree products (timber, honey, fruit, vegetables, fibres, fuel etc.). In many parts of Africa, wild fruit, firewood and charcoal are major sources of income, especially in times of crop failure. Ecosystems are also necessary for water purification, erosion regulation, waste treatment and disease regulation. Support services include soil formation (providing good soils for agriculture and vegetation). Degradation of these ecosystem services is threatening the achievement of the MDGs. About one sixth of the world population – a total of 1.1 billion people – remains without access to improved drinking water, and 84% of these live in rural areas. In addition, 2 of the 2.6 billion people without access to basic sanitation live in rural areas (UNICEF& WHO, 2006). The figure differs according to regions. For example, in 2004, in sub-Saharan African rural areas, the number of people who were not provided with improved drinking water was five times higher and those without access to sanitation were three times higher than those living in urban areas. Poverty is also much higher in the rural areas. In rural communities, water is required for drinking and agricultural purposes. Rainwater harvesting is highly decentralized and enables individuals and communities RAINWATER HARVESTING: A LIFELINE FOR HUMAN WELL-BEING 46 to manage their own water for these purposes. This is particularly suitable in rural areas with a dispersed population and where a reticulated water supply is not feasible or extremely costly for investment. The low cost of the rainwater harvesting technologies can be a more attractive investment option in rural areas. In addition to water for drinking and sanitation, fishing, animal husbandry and agriculture are the major activities in rural areas which all depend on a reliable water supply to be productive. As shown in Chapters 3 and 4, rainwater harvesting can also help meet the demands for water for these purposes. There are numerous cases where rainwater harvesting is used to improve livelihoods by providing water for domestic purposes; for subsistence and income generation activities such as gardening, and livestock rearing; for environmental purposes, through recharging groundwater and establishing woodlots to reduce deforestation. In essence, it can supply water to accelerate social and economic development, to alleviate poverty and generate income for rural farmers by enhancing the crop yield, modifying the method of production, as well as to promoting environmental conservation. Agro-pastoralists enhance livelihoods through better water supply in Kenya In Kaijado and Lare, in the semi-arid savannah of Kenya, rainwater harvesting provides water for drinking, sanitation, and enhancing the productivity of the agro-eco systems (Appendix II: Case 6.1). The technologies introduced consisted of roofwater harvesting for domestic purposes (drinking and sanitation), runoff collection in ponds for small gardens, trenches for groundwater recharge and afforestation. For sustainability, the project included a micro-finance component, where the community was trained to manage credits before borrowing money from commercial institutions. The project has enhanced the ecosystem functioning by recharging groundwater, increasing the volume of water stored, and reducing soil erosion through the family woodlots that reduced runoff-related erosion. Once the planted trees have matured, the women will use them for fuel, contributing to the reduction of deforestation, which is a major problem in the area. Family livelihoods improved from selling vegetables and income generation activities such bee-keeping and Working together to dig a run off RWH pond UNEP/Khaka

Modifying land management in order to improve efficiency of rainwater use in the African highlands.

Abstract: Water scarcity and drought in Africa are often in the news. The widespread tendency to relate farmers’ notion of drought to changes in the occurrence of dry spells is misguided: several recent studies have yielded little evidence of an increase in the length and/or frequency of such spells. The farmers’ concept of drought is contextual and an indirect result of land degradation. Plant production suffers because water is not available due to deteriorated physical properties of soil. Farmers’ perception of drought refers to the Green Water Use Efficiency (GWUE), i.e. the fraction of rain that is used for plant transpiration. GWUE in Africa is remarkably low: in sub-Saharan Africa, only 15% of the terrestrial rainwater is used by plants for the production of food, fodder and fibre. Although a millet crop grown under traditional circumstances uses only 50 mm in transpiration, the crop frequently suffers from agricultural drought due to excessive losses of rainwater. A range of land management practices is available to help improve GWUE. They can be classified according to their function. Hedgerow barriers and terraces can mitigate runoff; infiltration rates below hedgerows in Kenya were found to be three to eight times higher than where the crop was grown. Mulch that triggers soil fauna can improve water availability; mulching with straw from a local perennial grass in Burkina Faso doubled the water use efficiency from 1 kg mm−1 without fauna to 2 kg mm−1 with fauna. Water harvesting and water–nutrient synergy can improve water use; in case permeable barriers combined with the use of compost Sorghum yield in Burkina Faso was 2.3 times higher than in the control plots and the plots with the barriers only. Green water deserves more attention from policy makers, planners, land users, water engineers and managers.

Selection of suitable sites for water harvesting structures in Soankhad watershed, Punjab using remote sensing and geographical information system (RS&GIS) approach— A case study

Abstract: A case study has been conducted to identify suitable sites for water harvesting structures in Soankhad watershed, Punjab using information technologies such as Remote Sensing and Geographical Information System (RS-GIS). The IRS-1C, P6 satellite imagery of the Soankhad watershed was used. The various Thematic maps such as land use map, hydrological soil group map, slope map and DEM map were prepared for selecting suitable site for construction of water harvesting structures. The suitable sites were not found for nala bunding and farm ponds due to steep slope, less soil thickness and high runoff velocity. Fourteen check dams and six percolation tanks were proposed for the construction as per Integrated Mission for Sustainable Development (IMSD) guidelines. The water balance study of the Soankhad watershed was also computed with monthly mean temperature and rainfall data using TM model. The average runoff for the wet season (July–September) 1996 was computed to be about 1543.82 mm and the total runoff volume from the Soankhad watershed was estimated to be about 143.52 Mm3.

A probabilistic approach to rainwater harvesting systems design and evaluation

Abstract: Although rainwater harvesting system (RHS) is an effective alternative to water supply, its efficiency is often heavily influenced by temporal distribution of rainfall and water demand. Since natural precipitation is a random process and has probabilistic characteristics, it will be more appropriate to describe these probabilistic features of rainfall and its relationship with design storage capacity as well as supply deficit of RHS. This paper aims at developing a methodology for establishing the probabilistic relationship between storage capacities and deficit rates of RHS. A simulation model was built to simulate the input rainfall and water release in RHS. Historical rainfall records were then used as input for simulation and the results were used in probabilistic analysis for establishing the relationships between storage capacities and water supply deficits. The city of Taipei was used as study area for demonstration of this methodology and probabilistic distribution curves for storage capacity and deficit rate relationships were presented. As a result, a set of curves describing the continuous relationships between storage capacities and deficit rates under different exceedance probabilities were generated as references to RHS storage design. At a chose exceedance probability of failure, the engineer can decide from the curve on the storage size under a preset deficit rate.

Rainfed agriculture: unlocking the potential

Abstract: 1. Rainfed Agriculture - Past Trends and Future Prospects 2. Zooming in on the Global Hotspots of Rainfed Agriculture in Water Constrained Environments 3. Water Resource Implications of Upgrading Rainfed Agriculture - Focus on Green and Blue Water Trade-offs 4. Tectonics-climate Linked Natural Soil Degradation and its Impact in Rainfed Agriculture: Indian Experience 5. Determinants of Crop Growth and Yield in a Changing Climate 6. Yield Gap Analysis: Modeling of Achievable Yields at Farm Level 7. Can Rainfed Agriculture Feed the World? - An Assessment of Potentials and Risk 8. Opportunities for Improving Crop-water Productivity Through Genetic Enhancement of Dryland Crops 9. Water Harvesting for Improved Rainfed Agriculture in the Dry Environments 10. Supplemental Irrigation for Improved Rainfed Agriculture: In WANA Region 11. Opportunities for Water Harvesting and Supplemental Irrigation for Improving Rainfed Agriculture in Semi-arid Areas 12. Integrated Farm Management Practices and Up Scaling the Impact for Increased Productivity of Rainfed Systems 13. Challenges of Adoption and Adaptation of Land and Water Management Options in Smallholder Agriculture: Synthesis of Lessons and Experiences 14. Scaling-out Community Watershed Management for Multiple Benefits in Rainfed Areas.

Sustainability of rainwater harvesting systems in rural catchment of Sub-Saharan Africa

Abstract: Sustainability of rainwater harvesting in enhancing water productivity in various biophysical and socioeconomic conditions of SSA is a key in large scale livelihood improvement. A study was undertaken in Makanya catchment of rural Tanzania to assess sustainability of storage type of rainwater harvesting systems including microdam, dug out pond, sub-surface runoff harvesting tank and rooftop rainwater harvesting system. The increasing population in upstream areas of the catchment has forced use of RWH systems for streams and river water abstraction. The agricultural intensification in hillslopes has affected the water availability for downstream uses. Rainfall variability, runoff quality and quantity, local skills and investment capacity, labour availability and institutional support influence sustainability of rainwater harvesting systems.

Climbing the Water Ladder : Multiple-Use Water Services For Poverty Reduction

Abstract: In low- and middle-income countries, people need water for drinking, personal hygiene and other domestic use. But they also use it for livestock, horticulture, irrigation, fisheries, brickmaking, and other small-scale enterprises. Multiple-use water services (MUS) are best suited to meeting people’s needs. However, most water services are designed only for domestic water or only for agriculture, and fail to reflect its real-life use. The action research project ‘Models for implementing multiple-use water supply systems for enhanced land and water productivity, rural livelihoods and gender equity’ developed case studies in eight countries (Bolivia, Colombia, Ethiopia, India, Nepal, South Africa, Thailand and Zimbabwe) involving 150 institutions. The project analysed two models: homestead-scale and community-scale MUS and developed a ‘multiple-use water ladder' to show how better livelihoods flow from increased access to water. This book shows how livelihoods act as the main driver for water services and how access to water is determined by sustainable water resources, appropriate technologies and equitable ways of managing communal systems. Climbing the water ladder requires a small fraction of total water resources, yet has the potential to help people climb out of poverty. Local government can be the pivot to make this happen. But, it needs support to implement its mandate to meet multiple-use demand and to become more accountable to people in communities.

A GIS-based decision support system for rainwater harvesting (RHADESS)

Abstract: Rainwater harvesting (RWH) is an unconventional water source that is increasingly adopted in South Africa. Its implementation is promoted by non-governmental organisations and government programmes to alleviate temporal and spatial water scarcity for domestic, crop and livestock production and support the overall water resources management. Unreliable water supply is one of the elements central to the poverty level of rural population. As the potential of RWH to improve water access for drinking and other basic human needs is still untapped, the technique will spread further in the coming decades. Studies on the hydrological impacts of RWH are focused on plot scale and very little is known about its impacts at catchment scale. To integrate RWH into the development and management of water resources in South Africa, there is a need to develop tools and methodologies that not only assist planners with the identification of areas suitable but also quantify the associated hydrological impacts of its wide scale adoption. This paper presents the rainwater harvesting decision support system (RHADESS) that was built to assist decision makers and stakeholders by indicating the suitability of RWH in any selected part of South Africa and quantifying the potential impacts associated with its adoption at catchment scale. RHADESS is GIS-based and uses ArcView 3.3 as a platform to assess the RWH suitability of any given area of South Africa. Results are thereafter exported into an Excel spreadsheet that contains the hydrological impact, as runoff reduction, of different levels of adoption of RWH assessed by using the Pitman model. The decision support system guides the implementation of the following RWH categories: Infield RWH and ex-field RWH and domestic RWH. RHADESS was tested in two selected quaternary catchments C52A and V13D located in the Upper Orange water management area and the Thukela water management area, respectively.

Decentralized water management: rainwater harvesting and greywater reuse in an urban area of Beijing, China

Abstract: Large-scale centralised wastewater treatment system has often prevailed in industrial countries, and has been regarded as a successful approach during the last century. However, transfer of this highly water-consuming system and so-called ‘end-of-pipe’ technology to developing countries, especially in fast-growing cities with scarce water resources, has been extremely limited. Decentralized water treatment is not a new technology and has been successfully implemented in many rural areas worldwide. However, there are few applications in urban areas. This study at Tianxiu Garden in Beijing, China, investigated the potential and feasibility of water management based on a decentralized approach, but modified for application of greywater recycling and rainwater harvesting in a densely populated semi-urban area. A high degree of drinking water substitution (more than 25%) could not be attained by rainwater harvesting. Recycling of treated greywater for toilet flushing was shown to be an efficient method for min...