Showing papers on "Rainwater harvesting published in 2002"

Rainwater management for increased productivity among small-holder farmers in drought prone environments

Abstract: A critical analysis of conventional water resources assessments and re-visiting the on-farm water balance suggests large scopes for water productivity improvements in small-holder rainfed farming systems in drought prone environments of Eastern and Southern Africa. The paper addresses key management challenges in trying to upgrade rainfed agriculture, and presents a set of field experiences on system options for increased water productivity in small-holder farming. Implications for watershed management are discussed, and the links between water productivity for food and securing of water flow to sustain ecosystem services are briefly analysed. Focus is on sub-Saharan Africa hosting the largest food deficit and water scarcity challenges. The paper shows that there are no agro-hydrological limitations to doubling on-farm staple food yields even in drought prone environments, by producing more “crop per drop” of rain. Field evidence is presented suggesting that meteorological dry spells are an important cause for low yield levels and it is hypothesised that this may constitute a core driver behind farmers risk aversion strategies. The dry spell induced risk perceptions contribute amongst others to soil nutrient mining due to insignificant investments in fertilisation. For many small-holder farmers in the semi-arid tropics it is simply not worth investing in fertilisation (and other external inputs) as long as the risk for crop failure remains a reality every fifth year with risk of yield reductions every second year, due to periodic water scarcity during the growing season (i.e., not necessarily cumulative water scarcity). Results are presented from field research on small-holder system innovations in the field of water harvesting and conservation tillage. Upgrading rainfed production systems through supplemental irrigation during short dry-spells is shown to dramatically increase water productivity. Downstream implications of increased upstream withdrawals of water for upgrading of rainfed food production are discussed. Finally it is argued that some of the most exciting opportunities for water productivity enhancements in rainfed agriculture are found in the realm of integrating components of irrigation management within the context of rainfed farming, e.g., supplemental or micro irrigation for dry spell mitigation. Combining such practices with management strategies that enhance soil infiltration, improve water holding capacity and plant water uptake potential, can have strong impact on agricultural water productivity. This suggests that it is probably time to abandon the largely obsolete distinction between irrigated and rainfed agriculture, and instead focus on integrated rainwater management.

Pesticides in surface water, sediment, and rainfall of the northeastern Pantanal basin, Brazil.

Abstract: Within the last 25 years an intensive agriculture has developed in the highland regions of Mato Grosso state (Brazil), which involves frequent pesticide use in highly mechanized cash-crop cultures. To provide information on pesticide distribution and dynamics in the northeastern Pantanal basin (located in southern Mato Grosso), we monitored 29 pesticides and 3 metabolites in surface water, sediment, and rainwater of the study area during the main application season. In environmental samples, 19 pesticides and 3 metabolites were detected in measurable quantities, resulting in at least one pesticide detection in 68% of surface water samples (n = 139), 62% of sediment samples (n = 26), and 87% of rainwater samples (n = 91). Surface water samples were most frequently contaminated by endosulfan compounds (alpha-, beta-, -sulfate), ametryn, metolachlor, and metribuzin, although in low (< 0.1 microgram L-1) concentrations. Sediment samples exhibited concentrations up to 4.5 micrograms kg-1 of p,p'-DDT, p,p'-DDE, endosulfan-sulfate, beta-endosulfan, and ametryn. In contrast, rainwater was polluted with substantial amounts of endosulfan, alachlor, metolachlor, trifluralin, monocrotofos, and profenofos (maximum concentrations = 0.3 to 2.3 micrograms L-1) in the highlands. Lowland rainwater samples taken 75 km from the next application area contained 5- to 10-fold lower mean pesticide concentration than in the highlands. Cumulative deposition rates of the pesticide sum within the study period ranged from 423 micrograms m-2 in the highlands to 14 micrograms m-2 in the lowlands. The atmospheric input of pesticides to ecosystems seemed to be of higher relevance in the tropical study area than known from temperate regions.

Health Risks Associated with Consumption of Untreated Water from Household Roof Catchment Systems

Abstract: Rainwater harvesting is receiving increased attention worldwide as an alternative source of drinking water. Although collected rainwater is typically consumed without any type of disinfection, the microbial quality of this type of water source can be poor. Around the world, consumers of collected and stored rainwater may be at considerable risk to a variety of infectious diseases. This review presents studies attributing specific risks of diseases to the consumption of contaminated rainwater. Diseases attributed to the consumption of untreated rainwater include bacterial diarrheas due to Salmonella and Campylobacter, bacterial pneumonia due to Legionella, botulism due to Clostridium, tissue helminths, and protozoal diarrheas from Giardia and Cryptosporidium. Simple indicator systems such as fecal coliform measurements may prove to be inadequate for determining microbial risks associated with consumption of water from rainwater catchment systems.

Green roofs in temperate climates and in the hot‐humid tropics – far beyond the aesthetics

Abstract: Green roofs are still often seen as a pure aesthetical element in architecture, as a spleen of some “greenies”. In fact green roofs already contribute, to some extent, to a better microclimate through evaporation, filtering of dust from the air and a decrease in temperatures at the rooftop. In cities like Berlin and Munich many green roofs have already been realised. Coupled with this microclimate improvement, is the thermal comfort improvement under such roofs by more mass, dry or wet substrate, and shading through the plants. Besides improving the microclimate and the indoor climate, the retention of rainwater is another important advantage. That means an important reduction of the rainwater input in the sewage system during rainfalls, cutting the peak load, avoiding an overload of the system, which might cause flooding and serious health problems. The risk of flooding in cities, which is increasing in many cities due to a ground sealed by buildings, asphalt and concrete, can be diminished. One recent example of the use of green roofs with this purpose is the Potsdamer Platz in the centre of Berlin, where 100 percent of the rainwater has to be evaporated or used for toilet flushing on the building site. Scientific knowledge on green roofs is still limited to temperate climates, due to a development which took place in central Europe. Since 2000 a scientific project in Rio de Janeiro is checking local parameters, like possible vegetation, which can be used and substrate composition. Parallel to this, four prototype roofs, three greened and one blank, are used to measure the retention rate of the rain water and the temperature on the underside of the roofs in order to analyse the possible improvement of the thermal comfort in buildings. This paper will describe the scientific results of Germany and discuss the practicability on a larger scale under tropical conditions.

Fog-water harvesting along the West Coast of South Africa: a feasibility study

Abstract: Many parts of the West Coast of South Africa experience severe water shortages throughout the year. Despite the meager rainfall, however, the region is subject to a high incidence of fog which might provide water for water-poor communities. This paper investigates the fog water potential of the area. Since fog water collection rates are to some extent dependent upon the spatial and temporal characteristics of fog, these aspects were investigated. Pilot fog collectors were erected at six West Coast sites and the water collection rates measured over a three to four year period. It was found that the incidence of fog is mostly confined to the coastal zone below the 200 m contour line with fog frequency decreasing with latitude within this zone. The highest water collection rates were recorded at Cape Columbine where volumes in excess of 2.5 /m 2 of collecting surface can be expected to be collected per day. Of this, approximately 90% is due to fog deposition alone, while rainfall contributes to the remaining 10%. The quality of the water is good and fit for human consumption.

Innovative approaches to agricultural water use for improving food security in Sub-Saharan Africa

Abstract: This paper provides an overview of innovative options for developing and using water for food production in sub-Saharan Africa (SSA) in light of the growing scarcity and competition for water resources. These options include rainwater harvesting selective development of wetlands for agriculture exploitation of shallow groundwater and recycling urban waste. The options are largely based on low-cost individualized technologies which lend themselves to private-sector promotion. Water-demand management approaches are also discussed. (authors)

The Contribution of Drinking Water towards Dental Fluorosis: A case study of Njoro Division, Nakuru District, Kenya

Abstract: This study was carried out to measure the fluoride levels of water consumed in the Njoro division of Nakuru district, Kenya. The sources of drinking water, methods of water storage and utilisation, as well as the perceptions of the local community towards dental fluorosis and the percentage of children with moderate to severe dental fluorosis were also determined. Rainwater had mean fluoride levels of 0.5 mg L-1, dams 2.4 mg L-1, wells 4.1 mg L-1, springs 5.5 mg L-1, and boreholes 6.6 mg L-1. Water stored in plastic and cement containers did not show appreciable reduction in fluoride content with storage time; water stored in metal containers reduced fluoride by up to 8.2%; water stored in clay pots had the highest reduction in fluoride content, ranging between 34.3 and 64.7%;. Forty eight point three percent of children observed in the area had moderate to severe dental fluorosis, even though most people in the area did not know the cause of the problem.There is need to educate the community on the causes of fluorosis, and to lay strategies for addressing the issue, such as encouraging more rainwater harvesting, treating drinking water with alum, or using clay pots for storage of drinking water.

Preventing and Resolving Water Use Conflicts in the Mount Kenya Highland–Lowland System through Water Users' Associations

Abstract: In recent decades, the Mount Kenya highland–lowland system, which includes the Ewaso Ngiro North Basin, has experienced complex ecological and socioeconomic dynamics. These are reflected in changing land use systems and practices as well as in a rapidly growing human population, especially in the footzones and adjacent lowlands. These changes have exerted unremitting pressure on water resources, especially because the demand for water by different user groups has continued to grow, against the backdrop of expensive alternative sources (rainwater and groundwater harvesting) and increasingly dwindling river water resources. As each of the user groups moves to make substantial claims to available river water, competition for the resource becomes even sharper, thus setting the stage for conflicts related to scarcity that intensify during the dry season, at times resulting in fatal physical conflicts among different user groups in the basin, especially between upstream and downstream users. Different approaches have been used to address these scarcity-related conflicts. The present article discusses Water Users' Associations as one of the most effective initiatives launched to address the problem of water use conflicts in the basin in the recent past.

Runoff water management technologies for dryland agriculture on the Loess

Abstract: SUMMARY Arid and semi-arid environments undergo periodic seasonal agricultural droughts of varying extents and duration, erratic and ineffective rainfall of high intensity and short duration, with high surface runoff. High efficiency water-harvesting agriculture has been routinely used in the Loess Plateau agricultural production of China over the past 10 years. Localized habitat effect and regional water resource enrichment are the theoretical basis of high efficient water-harvesting agriculture. Features of this agricultural system are described, including: water harvesting of surface runoff from roads and collection in concrete yards on plastic sheets; water storage cellar tanks for harvesting runoff to provide life-saving/critical irrigation, with devices for water lifting and conveying such as hand pumps and pipelines; feasible methods of water use for limited supplies such as drip, hole, subsoil, and super-sheet irrigation; agronomic measures of high water use efficiency; and field micro-catchment f...

Rainwater Composition and Acidity at Five Sites in Malaysia, in 1996

Abstract: Rainwater chemical composition and acidity were determinedfrom weekly-averaged wet-only rainwater samples collected atfive sites in Malaysia throughout 1996. The major aim of thiswork was to assess the extent to which acid deposition, foundpreviously at one site in the Klang Valley, was a general,rather than local, phenomenon. To this end, three measurementsites were located spanning the length of the Klang Valley (anurban-industrial region of approximately 3000 km2containing the Malaysian capital, Kuala Lumpur). A fourth sitewas located outside, but adjacent to the Klang Valley, and thefinal site was located 300 km to the southeast, in anurban/industrial region adjacent to Singapore. Annual pHvalues in the range 4.16–4.40 and estimated total depositionfluxes of acidic sulfur and nitrogen species in the range 120–350 meq m-2 yr-1 show all sites to be impactedsignificantly by acidic deposition. Average contributionswere 60% as sulfur species, 40% as nitrogen species. Theresults confirm that potentially significant levels of aciddeposition occur in Malaysia as a regional phenomenonassociated with urban/industrial activities.

Chemical composition of rainwater around an industrial region in Mumbai

Abstract: Chemical analysis of rainwater samples collected at Kalyan, a downwind location of a large industrial belt, and at Alibag and Colaba, the upwind locations, during the southwest monsoon seasons of 1994 and 1995 and comparison with similar data of 1973-74 reveal that pH of rainwater at Kalyan which was alkaline 20 years ago became acidic due to long-term effect of pollutants A decreasing trend in excess SO4 was observed at Colaba and Kalyan, which is attributed to the pollution control measures adopted by industries and switching over from coal to natural gas which contains low sulphur Whereas the increasing trend in NOx observed at Kalyan and Colaba, is attributable to increased automobile emission

Water and the environment: a natural resource or a limited luxury?

Abstract: The risk of contamination of drinking water supplies with microbial pathogens is minimised by modern approaches to water management, but continues to be the major public health concern. Chemical contaminants usually pose little health risk except at very high levels, but debate continues over the potential adverse health effects of low-level, chronic exposure to compounds such as disinfection byproducts. Recreational water contact can be associated with adverse health outcomes either from microbial infections or exposure to cyanobacterial toxins. Environmental issues such as increasing salinity and global warming are likely to affect the sustainability of our current drinking water supplies and increase the threat of waterborne disease outbreaks. New technologies, use of alternative water sources, such as rainwater tanks, water reuse and restrictions will undoubtedly be part of the solution to our diminishing water resources, but have the potential to introduce new health threats.

Mitigating the potential unintended impacts of water harvesting 1

Abstract: Different forms of water harvesting have been used successfully in semi-arid areas of India for millennia as a means of protecting domestic water supplies and increasing or stabilising agricultural production. In recent years, water harvesting both in field (e.g. contour bunding) and along drainage lines (e.g. check dams) has been promoted and funded on a massive scale as part of different government and non-government programmes. Accepted wisdom is that rainfall should as far as possible be harvested where it falls and that these technologies are totally benign. However, evidence is emerging that water harvesting in semi-arid areas, if used inappropriately, can lead to inequitable access to water resources and, in the extreme, to unreliable drinking water supplies. Water balance studies in Andhra Pradesh and Karnataka have shown that water harvesting programmes impact significantly on patterns of water use and that this can result in distinct winners and losers. Winners include people who have improved access to water for productive purposes (e.g. irrigated agriculture) and losers include people whose access to water for domestic, productive and other purposes is reduced. It is also clear that livelihood gains experienced by some “winners” can dissipate as competition for water resources increases and traditional drought coping strategies become less viable and/or increasingly expensive. The recommendation from the analysis presented here is that water harvesting should be encouraged but within an integrated or adaptive water resources management framework using procedures that weigh up the benefits and tradeoffs associated with altered patterns of water use. The aim being identify potential unintended impacts so that, if at all possible they are avoided altogether, but if these do occur, they are recognised at an early stage and steps are taken to mitigate their affects.

Field and Laboratory Evaluation of Habitat Use by Rainwater Killifish (Lucania parva) in the St. Johns River Estuary, Florida

Abstract: I examined the relative importance of beds of tapegrass (Vallisneria americana) and adjacent unvegetated habitats to juvenile and adult (6-35 mm standard length) rainwater killifish (Lucania parva) over a large spatial scale within the St. Johns River estuary, Florida. Abundance of rainwater killifish did not differ between oligohaline and tidal freshwater portions of the estuary and this species was relatively rare at opposite ends of the St. Johns River estuary. The presence of rainwater killifish at a given site was determined in part by large-scale variation in environmental factors such as habitat complexity and salinity. When present at a site, rainwater killifish were found almost exclusively in structurally complex beds of tapegrass. Behavioral observations in the laboratory indicated that rainwater killifish pre- ferred vegetated over unvegetated habitats in the absence of both potential prey and predators and that use of vegetated habitats increased further upon addition of predatory largemouth bass (Micropterus salmoides). A laboratory predation experiment indicated that survival of rainwater killifish exposed to largemouth bass was significantly higher in vegetation than over open sand. Strong preferences for structurally complex vegetation likely reflect an evolved or learned behav- ioral response to risk of predation and help explain habitat use of rainwater killifish in the St. Johns River estuary.

Economic, Water Quantity and Quality Results from a House with a Rainwater Tank in the Inner City

Abstract: A dual water supply system (rainwater and mains water) has been installed at an old house in Maryville a inner city suburb of Newcastle in New South Wales, Australia. A design was developed for the installation of a rainwater tank to supply rainwater for toilet, hot water and outdoor uses. The rainwater supply is supplemented with mains water via a trickle top up system when water levels are low in the tank. An air gap is used for backflow prevention in accordance with Australian standards. The design, construction and performance of the dual water supply system at the Maryville house are examined in this paper. Monitoring of water quality from the rainwater tank and from an instantaneous hot water service at the Maryville house has revealed that the rainwater was acceptable for hot water, toilet and outdoor uses. Rainwater used in the hot water service was compliant with Australian drinking water standards. The cost of rainwater has been found to be $0.3 per kL which is less than the price of mains water in the Lower Hunter region and the commonly assumed cost of $1 to $14 per kL.

Rainwater Tank Options for Stormwater Management in the Upper Parramatta River Catchment

Abstract: This study investigates the extent to which rainwater tanks reduce the amount of on-site stormwater detention (OSD) storage required to satisfy the Upper Parramatta River Catchment Trust's (UPRCT's) OSD policy. In view of the limitations of the design storm approach, a continuous simulation approach was adopted. The DRIP stochastic rainfall model was linked with an allotment water balance model to evaluate different allotment scenarios using a 1000-year synthetic pluviograph record. The DRIP model was calibrated to a 53- year pluviograph located at Ryde. Comparison with statistics not used in calibration showed that DRIP performed satisfactorily. In particular good agreement with observed intensity-frequency-duration (IFD) curves was obtained, whereas AR&R IFD curves consistently underestimated the observed IFDs. Scenarios involving combinations of OSD, using 10kL rainwater tanks with 0 and 5 kL of detention storage were examined. For allotments with single dwellings between 50 to 70% of the tank volume can be counted towards the allotment's OSD volume. For a townhouse development this percentage varied between 36% and 53%. Rainwater tanks used in the single dwelling and townhouse scenarios are expected to reduce mains water consumption by 39% - 30% and 32% - 27% respectively. The variation depends on the number of occupants and the amount of tank airspace reserved for detention storage and the fraction of allotment drained by the rainwater tank(s).