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Water Resources Engineering
Published in P.K. Jayasree, K Balan, V Rani, Practical Civil Engineering, 2021
P.K. Jayasree, K Balan, V Rani
Agricultural water resource management covers a wide range of agricultural systems and climatic conditions, drawing on varying water sources, including surface water; groundwater; rainwater harvesting; recycled wastewater; and desalinated water. It also operates in a highly diverse set of political, cultural, legal, and institutional contexts, encompassing a range of areas of public policy: agriculture, water, environment, energy, fiscal, economic, social, and regional. Future policies to address the sustainable management of water resources in agriculture will be greatly influenced by climate change and climate variability, including seasonality problems, such as changes in the timing of annual rainfall patterns or periods of snow pack melt. In some regions, projections suggest that crop yields could improve. For other localities, climate change will lead to increased stress on already scarce water resources, while some areas are expected to see the growing incidence and severity of flood and drought events, imposing greater economic costs on farming and the wider economy. Irrigated agriculture, which accounts for most water used by agriculture, will continue to play a key role in agricultural production growth. To avoid a global water crisis, farmers will have to strive to increase productivity to meet growing demands for food, while industry and cities find ways to use water more efficiently.
Water Use and Availability
Published in Frank R. Spellman, The Science of Water, 2020
In the United States, in order to meet increasing biofuel demands, agriculture will require greater land and water resources. This will likely required: (1) conversion of existing cropland to grow biofuel corps: (2) changes in other land uses (like forest and pastureland) to grow biofuel crops; and (3) increasing the use of fertilizer and agrochemicals. Ultimately, all these actions will heighten potential agricultural impacts on natural resources. If local agriculture shifts to biofuel/bioenergy crops that required more than current agricultural water supplies, there is a likelihood of deleterious impacts on limited water resources. To be sustainable, bioenergy production must conserve and protect natural resources, including freshwater. The bottom line: Future trends in biofuels markets may have important consequences for U.S. agricultural water supplies.
The energy transition
Published in Arjen Y. Hoekstra, The Water Footprint of Modern Consumer Society, 2019
An increase in the demand for food in combination with a shift from fossil energy towards bioenergy will put additional pressure on the world’s freshwater resources. In many parts of the world, agricultural water demands already compete with the water demands from households, municipalities and industries, while the aquatic environment shows signs of degradation and decline. The EU, the USA, Brazil, China and various other countries have set targets to partially replace petrol by biofuels. When agriculture grows crops for bioenergy, however, the appropriated land and water cannot be used for producing food anymore. If previously unexploited land and water resources are used for producing biomass for energy, this will subtract from the amount of land and water available to sustain natural vegetation or from the amount of water that flows through our rivers and sustains river-dependent ecosystems and communities. Large-scale cultivation of biomass for the substitution of fossil fuels increases future water demand (Berndes, 2002). An important question is whether we should apply our freshwater resources for the production of bioenergy or food. The World Bank recognizes biofuels production as a major factor driving food prices. It estimates that 75 per cent of the increase of food prices in the period 2002–2008 was due to biofuels (Mitchell, 2008). Higher food prices may lead to decreasing food security for the poor.
Moving beyond ‘more crop per drop’: insights from two decades of research on agricultural water productivity
Published in International Journal of Water Resources Development, 2021
Meredith Giordano, Susanne M. Scheierling, David O. Tréguer, Hugh Turral, Peter G. McCornick
With growing water scarcity in many parts of the world, increases in agricultural water productivity seem to be desirable as a means to reduce overall water use in the agriculture sector. However, whether gains in water efficiency or productivity measured as single-factor productivity metrics are a relevant indicator at different scales of analysis and in different settings, or whether they contribute to broader development objectives, depends on a number of complex and interrelated factors, and requires more detailed analysis in those specific settings. The adoption of the SDGs in 2015, with the emphasis on increasing water-use efficiency across all sectors, provides an important moment to revisit the concepts of water efficiency and productivity, their use and limitations, particularly in relation to water savings. The insights of the previous section should be helpful in further operationalizing the implementation of the SDGs.
Assessing groundwater storage anomalies in Beijing based on the new multifactor-quantitative joint prediction model
Published in Human and Ecological Risk Assessment: An International Journal, 2023
Qingqing Wang, Wei Zheng, Wenjie Yin, Aiping Feng, Guohua Kang, Yifan Shen, Gangqiang Zhang, Shuai Yang
Notably, the MQPM model proposed in this paper also exists certain restrictions. Climate change is the main supply of groundwater recharge, which impacts the trend and seasonality of GWSA. Climate change consists of precipitation and ET; thus, the uncertainty of predictive rainfall and ET will affect the accuracy of GWSA. The ideal scenario is to collect plenty of observed points and distinguish unconfined and confined aquifers. However, the distribution of monitoring wells is sparse and uneven, and the specific yield used in this paper is estimated empirically. In the absence of specific yield with spatial distributions, GWSA are estimated by multiplying GWL changes by the fixed specific yield (Havril et al. 2018; Butler et al. 2020). The ranges of specific yield (μ) and storage coefficient in the North China Plain are 0.025–0.290 and 0.0004–0.0045, respectively (Zhang et al. 2009). The specific yield in Beijing is in the range of 0.065–0.14. Therefore, we assume 0.081 as the average μ in this paper, which is also used in Long et al. (2020). The monthly errors of GWSA estimation from observations are quantified by assuming a ±20% (Figure 5) uncertainty of the specific yield by referring to the studies of Huang et al. (2015), Pan et al. (2017), and Zhang et al. (2021). This work does not discuss the interactions between runoff and groundwater, including concentrated recharge from ephemeral rivers and base flows. About 80% of agricultural water use is derived from groundwater, and the remaining 20% is derived from reclaimed water. The reclaimed water can infiltrate into the aquifers and change the groundwater quantity and level, which are also neglected due to relatively small reverses.