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An array of methodologies to quantify blue, green, and grey water have emerged in recent years and are still evolving rapidly, as are efforts to come up with reliable indicators of human appropriation of freshwater resources. This study provides an overview of recent blue, green, and grey water quantification approaches by analyzing publications extracted from the Web of Science database utilizing the Network Analysis Interface for Literature Studies (NAILS) bibliometric analysis tool, covering the period 2000-2018. A steep increase in the number of blue, green, and grey water publications was observed from the year 2009, with the United States and China among the top contributing nations. Blue, green, and grey water quantification approaches used in the analyzed publications were broadly categorized into Water Footprint Assessment, Life Cycle Assessment, and Hybrid methodologies. The Water Footprint Network was the most influential hub in terms of providing the most productive and cited authors. “Water footprint” and “virtual water” were unsurprisingly the trendiest and most cited keywords associated with the sample of analyzed publications. The study provides important insights that are helpful in understanding the diversity of techniques that have been applied to quantify blue, green, and grey water in recent assessment studies.
Florida has successfully irrigated agricultural crops with reclaimed water (RW) for more than 50 years. Florida and California are the two largest producers and users of RW in the U.S. To allay early fears about RW, Florida regulatory agencies established rules in the 1980s that prohibited direct contact of RW with crops that are not processed but eaten raw. This means that RW cannot be used for direct contact irrigation or frost protection of crops such as strawberries or blueberries. Other states do not have such limitations on RW use. Reclaimed water has an excellent safety record, and no health problems have occurred from its use. The main edible crop that uses RW in Florida is citrus. Reclaimed water contains some macro- and micronutrients, but can provide only a small amount of nitrogen (N) to citrus. Some RW sources can provide adequate N to turf grass. Reclaimed water production has increased dramatically in the past 20 years, and much of the increased flow has gone to public access irrigation. While still important, agricultural use of RW as a percentage of total flow may continue to decrease, but the supply of RW continues to grow as Florida’s population increases.
Potential for use of recycled water1 is great, especially for agricultural irrigation, which comprises by far the highest percentage of water taken from developed sources in the arid and semi-arid regions of the world. In California, 80% of developed water is used for agriculture, and the same pattern prevails throughout the western United States. The potential for recycled water use in agriculture remains underrealized because of numerous impediments. Understanding how the incentives and impediments to agricultural reuse vary based on local context is critical to understanding the tradeoffs and technology requirements for different end uses of recycled water. Public perceptions about the safety of reclaimed water (from human waste) were a major impediment to water recycling until recent years. Several pioneers of water recycling have demonstrated—as specialists in the field of social psychology have hypothesized— that these attitudes are ephemeral and can be changed with proper outreach, demonstration, and education. Another impediment is the regulatory structure in some states. Water rights issues are another impediment specific to some western states in the United States. Cost differences for delivered water from traditional sources versus recycled water can be another challenge potentially requiring financial incentives in the interest of the greater good. One other impediment to the use of recycled water for agricultural irrigation is competition with other demands for the same water—landscape, golf course, industrial, and potable reuse. Potential for increased use of recycled water is great if impediments are removed and incentives are provided at the local, state, and/or federal levels to close the gaps (geographic and otherwise) between the utilities and the farmers.
Nonpoint source (NPS) pollution from agricultural and urban development is a primary source of nutrients and decreased water quality in aquatic systems. Installation of best management practices (BMPs) within critical source areas of the watershed can be helpful at reducing the transport of nutrients to waterbodies; however, prioritizing these areas may be difficult. The objective of this study was to develop several potential frameworks for prioritizing subwatersheds using baseflow water chemistry data in relation to a simple human development index (HDI; total percent agriculture and urban development). At a monthly interval, samples were collected at 26 sites throughout the Oklahoma portion of the Lake Wister Watershed (LWW) and analyzed for total nitrogen, total phosphorus, total suspended solids, and chlorophyll a. Changepoint analysis for each parameter found significant thresholds for each of the parameters ranging from 20 to 30% HDI. Changepoint analysis summary statistics were used to develop prioritization frameworks for the LWW that could be used to target subwatersheds where BMP installation would have the greatest effect at improving water quality. Additionally, regression models developed from the relationships between water quality parameters and HDI values serve as realistic targets for improving water quality, with the modeled line representing the target concentration for a given HDI value. After BMPs have been implemented, baseflow monitoring should continue at the subwatershed scale to track changes in water quality. Focusing monitoring efforts at the subwatershed scale will provide an earlier indication of the effectiveness of BMPs, as it may take several decades to detect improvements in water quality at the larger watershed scale.
Perhaps the biggest challenge the world faces is providing sufficient, nutritious, and safe food at the right time for its ever-increasing population. Considering current world population growth trends, it is estimated that the global population will be about 10 billion by the year 2050. Therefore, food production should at least double in the same period if food security is to be satisfied. Water and land resources play a pivotal role in agriculture and directly connect to food security. At the same time, the capacity to produce food is constrained by global climate changes and increased pressure on land resources. These challenges are more severe in Southern Asia, Sub-Saharan Africa, and East Asia, where conflict and lack of capacity to fund agricultural research and food production are common. Strategies that simultaneously increase food production and reduce threats to food security are therefore needed. The objectives of this paper are to review the grand challenges of global food security and to propose strategies for mitigating food insecurity, with an emphasis on the link between water resources and food production.
Due to its multiple uses, water is a highly competed-for resource. While the competition is mainly in the use of the resource, contestation over water resources is also demonstrated through how the resource is defined and described. Terms such as water stress and water scarcity are commonly used in literature, and so are various colors that define water quality, including white, grey, yellow, and black water. Water that is useful for agriculture is distinctly known as blue or green water, with the latter increasingly gaining prominence in water planning for improved agricultural productivity. Proper management of green water has been shown to improve grain yields in Sub-Saharan Africa by as much as 2.5 – 6 times. The arid nature of Sub-Saharan Africa, coupled with the high evapotranspiration rates, calls for improved management of green water, including reducing evaporation losses, reducing seepage, and increasing the water holding capacity of soils. The value of green water management in Sub-Saharan Africa is further enhanced by its low-cost nature when compared to irrigation, which is an area that Sub-Saharan Africa has also been focusing on as part of the solutions to the increasing food needs of its growing population. Infrastructure for irrigation is costly and not affordable to the majority in Africa. In addition, irrigation can only benefit those communities near the water sources, whereas proper green water management can have benefits to all communities, including those far from a water source.
This article examines policy innovations and data concerns related to water trading in Colorado, and develops econometric models of transactions occurring over two distinct time periods. The Punctuated Equilibrium Theory (PET) of policy adaptation is used to examine shifts in Colorado water trading policy paradigms. Creating better policy frameworks for water trading is a key concern for agricultural, urban, and environmental water interests, given hotter temperatures and more variable precipitation patterns in the western U.S. Contractual arrangements of varying types are being used to engage farmers in providing reliable water supplies for ecosystem and urban needs through changes in farm water use practices. While various pieces of information about changes in water use can be gleaned from public databases, transaction price information is notably lacking. Recent Colorado policy innovations related to water trading emphasize reducing on-farm consumptive use and making water available for other purposes without permanently drying up irrigated cropland. The use of econometric models analyzing water rights transactions provides insight into how changes in key external factors affect transaction prices. The econometric models developed here focus upon Colorado’s urbanizing Front Range and examine the effect of demographics, housing prices, drought indicators, and agricultural profitability on prices at which water is traded. Volume traded, drought measures, housing prices, alfalfa prices, and water source characteristics are statistically significant in these models. The article concludes by discussing factors that contribute to water trading policy innovations
and the broader relevance of Colorado’s innovative trading arrangements to water management challenges
in arid regions.
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