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Not Available ; We are writing in response to the article by M Dinesh Kumar, Ankit Patel, R Ravindranath, O P Singh "Chasing a Mirage: Water Harvesting and Artificial Recharge in Naturally Water-Scarce Regions" (EPW, 30 August 2008). The authors have argued that runoff water harvesting does not offer any potential for groundwater recharge or for improving water supplies at the basin scale. They have, thus, concluded that the investments made on this sector are a colossal waste of scarce resources and also cause several negative social and environmental consequences. However, in the conclusion they say, "The foregoing analysis does not suggest that water harvesting and groundwater recharge systems do not generate benefits", thus indicating an iota of doubt. In the process of analysis, some of the implicit underlying assumptions made by authors include: (1) Comparison of annual rainfall with annual reference/potential evapotranspiration is the guiding principle/indicator for runoff water harvesting. (2) Water harvesting is essentially and in all instances meant for groundwater recharge. (3) Runoff is the amount in excess of the soil moisture storage and infiltration. (4) Watershed programmes only have problems of quality of implementation. (5) Water harvesting systems are, by and large, designed to capture the entire runoff and state government and central developmental agencies alongwith nongovernmental organisations (NGOs) are promoting the concept. (6) The existing storage and diversion capacities in river basins is close to utilisable flows. (7) Water harvesting necessarily has to be profit-oriented and in order to make it happen it has to be utilised for high value crops. (8) Reliability of supplies from water harvesting systems is very poor in arid and semi-arid regions of India, which are characterised by low mean annual rainfalls, very few rainy days, high inter annual variability in rainfall and rainy days and high potential evapotranspiration. (9) In order to call water harvesting systems profitable, the incremental benefits by water harvesting systems have to be beneficial at basin scale but not at the local level. In the light of these assumptions and the consequent analysis branding water harvesting systems as ineffective, we would like to offer our comments. India has a long history of water harvesting which has been neglected after the creation of large storage structures and popularisation of borewell technology. However, the revival of the water harvesting systems by individuals, NGOs, and developmental agencies, has led to their importance being recognised particularly in arid and semi-arid rainfed areas. Water harvesting systems were started as part of catchment area treatment in river basin projects to act as complementary storage structures and to reduce the silt movement which otherwise would reach the reservoir leading to siltation and reduction in effective storage over a period of time. ; Not Available

This is a conference paper. ; The state of Maharashtra in India, covers an area of 307,713 sq. km. and supports a population of over 82 million people. Over half of this population is rural. The government of Maharashtra has identified 20,000 villages, which face problems related to water. In these villages conventional sources like open dugwells, borewells and piped water supplies fail due to depleting water tables, poor water quality or the high costs involved in operation and maintenance. Many of these villages are supplied by water tankers, especially during the dry pre-monsoon. Water supplied by tankers is prone to pollution, as well as extremely expensive.

Collective action for water harvesting irrigation (WHI) refers to the joint or collective effort of farmers in getting and using water for crop, animal, household, or other purposes. Organized water user groups also handle external representation with government programs and external demands (either competing or complementary) for water and other resources. In water-scarce areas, the goal is for farmers to produce high crop yields with less water, which can be achieved when farmers collectively manage the water resources available to them. ; Non-PR ; IFPRI4; CAPRi ; EPTD

Die Studie gibt Empfehlungen zur ökologisch tragfähigen Gestaltung eines Gemeinschaftsgartens in einem Sahel-Dorf.

Roof water harvesting is being widely promoted as a panacea for the growing drinking water crisis in India and many underdeveloped and developing countries. This article analyzes the scope, physical feasibility, and economic viability of roof water harvesting systems across classes and under different physical and socioeconomic situations. This article argues that roof water harvesting systems (RWHS) are not alternative to public systems in urban and rural areas of regions receiving low rainfall. Hydrological opportunities for RWHS are very poor in urban and rural areas. The systems offer very little scope in ensuring domestic water security for urban housing stocks of low- and middle-income groups. At the same time, they offer tremendous potential for independent bungalows having large roof area. However, their physical feasibility is very poor in urban areas. Their economic viability as a supplementary source of domestic water supply seems to be poor in urban areas, when compared to augmenting the supplies from the existing public systems. The incredibly low rates charged for domestic supplies by urban water utilities and government subsidies for RWHS would only lead to the urban elite increasing their access to water supplies, while the burden on water utilities would remain unchanged. This will lead to greater inequities in access to water supplies. At the same time, in rural areas with dispersed populations and hilly areas, RWHS may be economically viable as a supplementary source to already existing public water supply schemes. But as its impacts are not likely to be uniform across classes, government subsidies are not desirable. In hilly regions receiving high rainfalls, government investment for community water supply schemes could be replaced by heavy subsidies for installation of RWHS.

Khartoum State in Sudan is subject to the erratic and intense rainfall during the short rainy season and dryness and heat throughout the rest of the year. High intensity rainstorms with a short duration have become more frequent in the area during the last two decades resulting in cities inundation and flash floods in the rural parts. On the other hand, the dry season means hot weather in the urban parts and water shortage in the rural part. Rural areas are dependent on the runoff water brought about by the seasonal streams as a source of water. For this study, Khartoum City Center and Seleit area were taken to investigate the application of water harvesting in the urban and rural areas, respectively. Accordingly, the hydrological characteristics and the specification of the potential water harvesting sites and systems were examined. For Khartoum City Center, characteristics of the drainage system were examined using ArcGIS platform. It is found that the drainage system covers 42% of the area with total capacity of 24000 m3. Daily rainfall data for urban meteorological station were used to calculate the probability and the return period of the rainfall, as well as the potential runoff. Rainfall probability of occurrence was calculated applying Gumbel distribution method for extreme events that were arranged according to the Peak-over-Threshold method. The potential runoff that could be generated from a certain rainfall was calculated using the Natural Resources Conservation Services method provided by the United States Department of Agriculture (US-NRCS). Accordingly, the curve number was calculated depending on the land use/land cover and the hydrological soil group. Consequently, the weighted curve number is found to be 94%, indicating dominant imperviousness. 13.1 mm rainfall depth produces runoff volume equal to the drainage system capacity with return period of one year; whereas more than four folds the drainage system capacity is produced by 30 mm rainfall depth that is considered the threshold for raising flood hazard. Six potential sites for roof rainwater harvesting were selected. Accordingly, it is found that, the application of roof water harvesting in 18% and 72% of the commercial and business district buildings can accommodate the runoff resulting from the 13.1 and 30 mm rainfall depth, respectively. Hence, impounding rainstorm water would help managing the urban runoff water, and consequently, the stored water could be used for making more green areas that will enhance the urban environment. Three watersheds of ephemeral streams (wadi), namely Wadi El Kangar, Wadi El Seleit, and Wadi El Kabbashi make up Seleit area. Distinct maps were prepared in ArcMap for the calculation of the potential runoff and the specification of the appropriate water harvesting sites and systems. The Wadis watersheds areas are found to be 540, 344 and 42 km2 for Wadi El Kangar, Wadi El Seleit and Wadi El Kabbashi, respectively. Daily rainfall data of rural meteorological station were classified into three groups representing the soil dry (AMCI), moderate (AMCII), and wet (AMCIII) moisture conditions; the respective CNI, CNII, and CNIII values were calculated accordingly. The weighted CN values indicate high runoff potential within the three soil moisture conditions. Accordingly, the rainfall thresholds for runoff generation for AMCI, AMCII and AMCIII conditions are found to be respectively 18.3 mm, 9.1 mm and 4.4 mm for Wadi El Kabbashi and 22 mm, 11 mm and 5 mm for both Wadi El Seleit and Wadi El Kangar. El Kangar dam subwatershed was used for calibrating the potential runoff calculated by the NRCS method. Since the Wadis are ungauged, Google Earth and GIS platforms were used to calculate geometrically the volume of the dam reservoir water for three years. This volume was compared to the annual runoff calculated by the NRCS method. Consideration to different factors was made to locate the potential water harvesting sites. Accordingly, water harvesting systems for fodder and crop plantation; sand storage surface or subsurface dams; or groundwater recharge, were specified. The socio-economic study revealed that the financial capacity, if any, of the villagers is very limited. Thus, the financial source for the construction of the suggested potential water harvesting or the rehabilitation of the existing ones is questionable. Hence, other potential financial sources are needed to help executing water harvesting projects in the region, e.g. Khartoum State Government. Applying water harvesting in Seleit area is found to be promising. Improving the livelihood of the villagers by applying runoff water harvesting could assure better water accessibility, better income generation from farms production, and allocation of time for other activities, e.g. education. This would be reflected in reduced migration to nearby cities and stabilized market supply of agricultural and animal products. Therefore, the development of the rural part is of great benefit to the development of Khartoum State, as long as the interdependency and mutual benefit between the rural and urban areas, represented by the local food and labor market, remain exist.

AbstractNew sources of clean water are currently being researched and implemented, to face global water shortage. Techniques such as desalination or cloud seeding can have a high yield but present problems such as excessive energy consumption or consistent environmental impacts. Fog harvesting stands out for being considerably simpler and inexpensive compared to the previous. In the last decades researchers have developed detailed studies and numerical models, supported by a number of successful examples located mainly in arid or seasonally arid climates. This study surveys existing methods to collect water from fog, such as drop coalescence on vertically placed meshes, chemical absorption and desorption and radiative condensers. Yields from different collectors are compared and some considerations on influencing climatic factors are discussed, suggesting that radiative systems may be applied on building envelopes as collection devices. A follow‐up paper will present experimental results on applying radiative collection systems in buildings.

AbstractFog harvesting stands out as a simple and inexpensive form to produce drinkable water from alternative sources, when compared to other available techniques. This paper presents results from a set of experiments performed on radiative condensers, deemed as a promising system to be integrated in building envelopes, following a literature review on fog condensers presented in a previous work. An analysis of condensation potential obtained using high emissivity substrates and titanium dioxide nanocoatings is presented, as well as the influence of sample position and orientation, and impact of climatic variables. Finally, the role of nanotechnology in overcoming limitations of radiative systems is discussed as a means to increase harvesting efficiency with functionalized, engineered nano‐patterns on collector surface. Based on biomimicry principles, nanocoatings including nanoscale 3D optimal geometries are discussed, and the use of nanoimprint technology (NIL) is proposed to massively produce nano‐patterned panels with biomimetic fog capturing features.

Acidification of rain water in urban cities is playing major environmental issues. Acid rain is generally caused by the formation of sulphuric acid and nitric acid. These sulphur and nitrogen emission are resulted from different sources like industries, vehicles etc. Rain water is a major source for ground water recharge in urban and rural India, Government of India has already provided water policies in 1987 and 2002 for conservation of water with different technology of harvesting. Roof top rain water harvesting is a good practice to collect rain water and inject it directly in the ground without much contamination. Ministry of Environment and Forest (MoEF) suggested different design and material selection for rain water harvesting pits to remove the suspended particles and other impurities, however no provision of controlling the pH is provided for the acidic rain water. Hence the present study proposes modification in the existing rain water harvesting pit to neutralize the acidic pH from rain water.

Rain water harvesting (RWH) and Artificial recharge techniques are low cost solutions to water crisis. In cities, due to increasing urbanization, rain water can be harvested and recharged to the ground water artificially. This paper presents a study of effectiveness of RWH in terms of change of trends in aquifer behaviour. Chennai, formally Madras, City, capital of Tamil Nadu State is selected as the study area since major RWH structures has taken constructed during 2001-2003 because of Government legislation. Preliminary analyses of rainfall and groundwater levels were carried with respect to space and time to understand the trends. Water table contours were drawn using the Arc GIS.9.2 software. "Groundwater Estimation Committee (GEC)" rules of Government of India were used for estimation the change in storage during pre and post RWH periods, which are found to be 1.76 Mm3 & 32.77 Mm3 respectively. It is concluded that the implementation of RWH has improved the groundwater storage though the rainfall in the study area is decreased and the extraction is increased due to raise in population.