AN INSULATED EVAPORIMETER1

Evaporation was measured from a circular evaporation pan, 18 inches in diameter and 8 inches deep. The pan was insulated on the sides and bottom using 2 inches of freon-blown polyurethane foam. A U.S. Weather Bureau Class A evaporation pan was used to obtain reference evaporation measurements. Water evaporation from the Class A pan and the insulated pan were highly correlated. Using a water-methanol mixture, the insulated pan may be operated at temperatures below 32 F; the equivalent liquid water evaporation may be determined using a regression equation.     

PRICING IRRIGATION WATER IN DEVELOPING COUNTRIES1

ABSTRACT Alternative combinations of water pricing and regulations are possible in allocating irrigation water. The best combination will depend on the value of water, ability to control deliveries, desire to subsidize agriculture, ownership traditions, crops grown, return flows, drainage problems, staff training, ability to collect fees, the number of farmers involved, etc. Marginal cost pricing is just one possible alternative and it is more a way of thinking about prices rather than a set system. The possibilities for achieving an equitable and efficient distribution of water are improved if some form of marginal cost pricing is included in the system of water charges.     

CLIMATOLOGICAL WATERSHED CALIBRATION1

ABSTRACT: This study tests the hypothesis that climatic data can be used to develop a watershed model so that stream flow changes following forest harvest can be determined. Measured independent variables were precipitation, daily maximum and minimum temperature, and concurrent relative humidity. Computed variables were humidity deficit, saturated vapor pressure, and ambient vapor pressure. These climatic variables were combined to compute a monthly evaporation index. Finally, the evaporation index and monthly precipitation were regressed with measured monthly stream flow and the monthly estimates of stream flow were combined for the hydrologic year. A regression of predicted versus measured annual stream flow had a standard error of 1.5 inches (within 6.1 percent of the measured value). When 10, 15, and 20 years of data were used to develop the regression equations, predicted minus measured stream flow for the last 7 years of record (1972–1978) were within 16.8, 11.5, and 9.7 percent of the measured mean, respectively. Although single watershed calibration can be used in special conditions, the paired watershed approach is expected to remain the preferred method for determining the effects of forest management on the water resource.     

生态脆弱地区水电的可持续开发

西部生态脆弱地区水电资源丰富,目前开发利用程度低,远远不能满足国民经济快速发展的需求.水电开发对生态脆弱地区的环境保护和社会经济发展具有重要的促进作用,加快西部生态脆弱地区水电资源开发是实现可持续发展的战略任务.     

Rice versus fish revisited: On the integrated management of floodplain resources in Bangladesh

Disproportionately little attention has been paid to the dry season trade‐off between rice and (inland capture) fish production on the floodplains of Bangladesh, compared to the same trade‐off during the flood season. As the rural economy grows increasingly dominated by dry‐season irrigated rice production, and floodplain land and water come under ever‐increasing pressure during the dry winter months, there is an urgent need to focus attention on these dry months that are so critical to the survival and propagation of the floodplain resident fish, and to the poor people that depend on these fish for their livelihood. This article examines three important dry‐season natural resource constraints to floodplain livelihoods in Bangladesh, and finds a common factor at the heart of all three: rice cultivation on lands at low and very low elevations. The article articulates the system interlinkages that bind these constraints and the long‐run trend towards irrigated rice cropping on lower‐lying lands, and suggests a management approach based on locally tailored strategies to arrest this trend. Apart from its direct relevance to the floodplains of Bangladesh, which support more than 100 million people, these lessons have relevance for river floodplain systems elsewhere in the developing world, notably the Mekong Delta.     

Capacity to Influence Sources of Heavy Metals to Wastewater Treatment Sludge

Wastewater treatment sludge contains valuable nutrients, yet represents a residue problem due to the amount of heavy metals, which is one of the factors preventing the use of sludge as fertilizer. In Sweden, the government has a declared aim of closing the ecocycles of nutrients to arable land, while at the same time the existing limit values are among the lowest in the world. This paper focuses on the opportunities for Swedish wastewater utilities (WWUs) to manage and reduce sources of heavy metals in order to get sludge approved and recycled. A case study focusing on sources of the heavy metals Cd, Cu, Hg, Ni, Pb, and Zn and the WWUs ability to influence the source by means of existing regulations was traced and categorized. A substantial fraction of the heavy metals were shown to be caused by diffuse emissions, such as the use of goods and products in society. For most sources discussed in the paper, a WWU can only manage the sources to a limited extent, if at all. This study shows that the WWUs cannot manage both recycling of nutrients and a decrease in heavy metals ending up in sludge. Diffuse emissions of heavy metals must be examined in context, not as a separate phenomenon or an issue for a single actor. The existing environmental legislation does not handle diffuse sources, yet long-term strategies for reducing the emissions to wastewater treatment must involve the reduction of diffuse emissions.     

Population,Development, and Waste Management in Botswana: Conceptual and Policy Implications for Climate Change

Based on government and other relevant documentation, this paper explores the conceptual linkage between population, development, and waste management in Botswana and the implications of this relationship for global climate change. Population is increasing, albeit at a decreasing rate. Spatially, the population is becoming more and more concentrated as the rates and level of urbanization increase. Economic growth has remained consistently high. The combined effect of population dynamics and economic development are having a noticeable imprint on the environment in the form of increased waste generation. Poor waste management poses a real threat to environmental sustainability in general and climate change in particular because of inadequate technology, weak institutional mechanisms to enforce regulations, and low levels of sensitization among the public to deal with the problem. Mitigation measures are suggested to minimize the negative effects of waste management on climate change.     

Local people's attitudes towards conservation and wildlife tourism around Sariska Tiger Reserve, India

Conservationists in the recent years view local peoples' support for protected areas management as an important element of biodiversity conservation. This is often linked to the direct benefits, which local communities get from the protected areas. These benefits could be in the form of biomass resources, park funds diverted to local villages by state agencies and revenue from wildlife tourism. There are a very few studies which have attempted to study the direct relationship between benefits from wildlife tourism and local support for conservation. In India, wildlife tourism is restricted, and mostly controlled by state and private agencies. Wildlife conservation policy does not view tourism in protected areas as a source of revenue for the local communities. The present study examines the local people's attitudes towards wildlife tourism and the impact of benefits from tourism on the local support for Sariska Tiger Reserve (STR), India. STR is a flagship for tourism where protected areas are increasingly being visited and where local support for wildlife tourism has not been studied adequately. Results indicate that two-thirds of the respondents were positive towards tourism and support for conservation. The respondents were aware that more tourism benefits are possible from a well-conserved protected area. There appears to be correlation between benefits obtained by local people from wildlife tourism and other sources, and support for protected area existence, suggesting that benefits impact people's attitudes towards conservation. Some of the main problems are the unequal distribution of tourism benefits, lack of locals' involvement in tourism and development. There is a need to clearly address these issues, so that protected areas may get the support of local people, which may lead to sustainable development.     

Environmental Control and Limnological Impacts of a Large Recurrent Spring Bloom in Lake Washington,USA

A series of statistical analyses were used to identify temporal and spatial patterns in the phytoplankton and nutrient dynamics of Lake Washington, an mesotrophic lake in Washington State (USA). These analyses were based on fortnightly or monthly samples of water temperature, Secchi transparency, ammonium (NH₄), nitrate (NO₃), inorganic phosphorus (IP), total nitrogen (TN), total phosphorus (TP), dissolved oxygen (DO), pH and chlorophyll a (chl a) collected during 1995–2000 from 12 stations. Lake Washington has a very consistent and pronounced annual spring diatom bloom which occurs from March to May. During this bloom, epilimnetic chl a concentrations peak on average at 10 μg/L, which is 3 times higher than chl a concentrations typically seen during summer stratified conditions. The spring bloom on average comprised 62% diatoms, 21% chlorophytes and 8% cyanobacteria. During summer stratification, diatoms comprised 26% of the phytoplankton community, chlorophytes 37% and cyanobacteria 25%. Cryptophytes comprised approximately 8% of the community throughout the year. Overall, 6 phytoplankton genera (i.e., Aulacoseira, Fragilaria, Cryptomonas, Asterionella, Stephanodiscus, and Ankistrodesmus) cumulatively accounted for over 50% of the community. These analyses also suggest that the phytoplankton community strongly influences the seasonality of NO₃, IP, DO, pH and water clarity. According to a MANOVA, seasonal fluctuations explained 40% of the total variability for the major parameters, spatial heterogeneity explained 10% of variability, and the seasonal-spatial interaction explained 10% of variability. Distinctive patterns were identified between offshore and inshore sampling stations. The results of our analyses also suggest that spatial variability was substantial, but much smaller than temporal variability.     

Effects of mechanical fracturing and experimental trampling on Hawaiian corals

In situ trampling occurred under experimental conditions to quantify the differences in the responses to anthropogenic trampling in four dominant species of Hawaiian corals, Porites compressa, Porites lobata, Montipora capitata, and Pocillopora meandrina. Trampling was simulated daily for a period of nine days at which time further breakage was minimal. Forty treatment colonies produced 559 fragments. Trampling was followed by an 11-month recovery period. Coral colony and fragment mortality was low. All four species were highly tolerant of inflicted damage, suggesting that some species of corals can withstand limited pulse events that allow time for recovery. Growth rates following trampling were significantly lower in the treatment groups for three of the four species. This study demonstrated that very few trampling events can produce significant changes in growth even after a long recovery period. Survivorship of fragments is clearly size- and species-dependent in M. capitata and P. compressa. Smaller fragments (<5 cm) had higher mortality than larger fragments (>5 cm). High breakage rates for M. capitata and P. compressa are consistent with the nearshore, low-energy regions they inhabit—the same environment frequented by skin divers and waders. Mechanical tests were conducted to determine tensile and compressive strengths. Pocillopora meandrina exhibited the strongest skeletal strength, followed in decreasing order by Porites lobata, Porites compressa, and Montipora capitata. The skeletal strength obtained from the experiments correlate with the wave energy present in the environments in the regions they inhabit, suggesting that structural strength of corals is an adaptive response to hydraulic stress.