Following a global trend, California has undergone a warming trend in recent decades with more rain than snow in total precipitation volume . Increasing temperatures are melting snowpack earlier in the year and pushing the snowline at higher elevations, resulting in less snowpack storage. The current trend is projected to become more frequent and persistent for the region. As a result, surface water supply is projected to erode with time, while the rainfall will experience increased variability, possibly leading to more frequent and extensive flooding . Rising sea levels will also increase the susceptibility to coastal and estuarine flooding and salt water intrusion into coastal groundwater aquifers . In California that sea level is estimated to rise between 150 and 610 mm by 2050 . As the reliability of surface water is reduced due to the effects of climate change, if water reclamation is not implemented with higher market penetration, the demand on groundwater pumping is expected to increase, resulting in higher energy usage for crop irrigation. Our calculations show that for every percent increase in groundwater pumping over 2015 values, the state would consume an additional 323 GWh y-1 of energy generating a net increase of 8 x 104 MTCO2E y-1 . This additional energy usage will amount to approximately 43.7 million USD for every percent increase in groundwater pumping applied to crop irrigation, calculated in 2015 dollars. Further research is warranted to determine the effect of climate change on carbon footprint associated with the energy requirements for irrigation water, particularly for crops grown exclusively for export and how this carbon emission compares with other societal compartments of the energy portfolio. A sensitivity analysis was performed to show the effect of variable k on the overall carbon footprint associated with the energy savings of applying reclaimed water in lieu of traditional groundwater pumping . For this analysis,blueberry container size the k values ranging between 0.3 and 0.7 kgCO2eq kWh-1 were used to account for the different k within a spatial domain analysed in our study.

Furthermore, this sensitivity analysis addresses the global drive to mandate increasing shares of renewables in power generation portfolios . For example, in 2011 California Senate Bill No. 2 requires electric service providers to increase procurement from eligible renewable energy resources from 20% to 33% by 2020 . In 1994, in its General Assembly meeting to combat desertification in countries experiencing serious droughts, the United Nations defined arid and semi-arid regions as areas having the ratio of annual precipitation to potential evapotranspiration within the range of 0.05 to 0.65 . According to this definition, regions in California and other Mediterranean countries such as Chile, Spain, France, Italy, South Africa and portions of Australia are classified as arid and semi-arid regions. Other regions of the world such as Central Asia, South Asia, East and Southern Africa, Central Africa and West Africa also meet this definition. The information presented in our research is intended to serve as a baseline for reference in areas sharing similar climate conditions as defined by the UNCCD. The study found that currently the use of reclaimed water application in California for the agricultural industry is very low, an average 1% for the period 1998 – 2010. For every percent increase in reclaimed water use in agriculture, the resulting energy saving is 187 GWh yr-1 , which at the current energy cost equates to more than 25 million USD. Aside from the energy saving and economic benefit, the application of reclaimed water for crop irrigation also produces a direct safeguard of 4.2 x 108 m3 in groundwater supply and a reduction in carbon footprint of 4.68 x 107 MTCO2E y-1 . If reclaimed water use increased from the current 1%, the energy savings, carbon footprint reduction, and economic benefits were calculated for both the current power generation portfolio and for the projected increase of renewable energy. Even in the scenario of a substantial reduction of CO2-equivalent emissions by meeting and exceeding targets for renewable energy, the increase in reclaimed water use would still provide a net carbon footprint reduction. Figure 4-7 shows the results of our model calculations. This research is intended to serve as a baseline reference and used as a planning tool to help water resources planners. Specific location, availability of reclaimed water supply, conveyance infrastructure and methods of treatment will influence the calculated results and associated costs presented.

Nonetheless, the results of this study furthers our current understanding on the role of reclaimed water on curbing groundwater withdrawal in an arid and semi-arid region like that of Southern California, by providing the context of its existing usage, estimated energy consumption, carbon footprint reduction, and potential monetary savings that can be realized. The trends observed in this study may be applicable to other regions of the world where water scarcity, energy costs, and climatic conditions require the use of reclaimed water as a sustainable water source.The research hypothesis tested true: in fact, the application of reclaimed water not only preserves groundwater resources but also decreases the energy footprint and carbon emissions associated with crop irrigation. The results show that there are savings in both groundwater supply and energy resources when applying reclaimed water for crop irrigation. For California, the average energy requirement for groundwater pumping was 0.770 kWh m-3 while reclaimed water production with gravity filtration was 0.324 kWh m-3 . Hence, the energy advantage of applying reclaimed urban wastewater for crop irrigation over groundwater pumping within this spatial domain would be 0.446 kWh m-3 . The calculated energy savings for applying reclaimed water in lieu of groundwater resulted in 57.9% reduction of energy usage. Annually, this amounts to approximately 187 GWh y-1 of energy savings for California, creating in a reduction of 4.68 x 107 MTCO2E of carbon emission. If reclaimed water use were increased from 1% to 5%, 10%, 15%, or 20%, the respective total energy savings, monetary savings and carbon footprint reduction would increase linearly. Based on the calculations, reclaimed water required the least amount of energy, whereas ocean desalination had an energy intensity approximately 11 times higher. When compared to traditional groundwater pumping, the energy intensity associated with water reclamation was discounted by 58%, highlighting the importance of reclaimed water as a potential competitive source. The results of this study further our current understanding on the role of reclaimed water on curbing groundwater withdrawal in arid and semi-arid regions.

The trends observed in this study may be applicable to other regions of the world where water scarcity, energy costs,growing raspberries in container and climatic conditions require the use of reclaimed water as a sustainable water source. Quantitative research in the field of exported water is still very much underdeveloped despite the many virtual water studies conducted over the years. The data presented in this research can serve as estimate but further research should address the uncertainty. Enhanced procedures to account for exported water and references should be developed and disseminated. These results highlight the need to consider water use efficiency in agricultural irrigation. Our findings suggest that California’s water resources are being exported outside its borders in magnitudes greater than that of the water consumed by the municipalities within the state. Thus, the state might be vulnerable to water-supply constraints if the trend continues indefinitely into the future. With better water management practices and sound public policies and increased investment in water infrastructure and efficiency, farmers and other water users can increase the yield of each water unit consumed. The current scenario appears to promote a positive feedback mechanism of resource draining resulting in environmental consequences for California’s water resources. California agriculture under growing pressure of water is beginning to explore innovative uses of reclaimed water. Some growers already use reclaimed wastewater in different ways, depending on the level of treatment the water receives. Most common is the use of secondary treated wastewater on fodder and fiber crops. Increasingly, however, growers are irrigating fruits and vegetables with tertiary-treated wastewater producing high-quality crops and high yields. Wong et al., reported that the Cities of Visalia and Santa Rosa have developed projects to irrigate more than 6,000 acres of farmland including a walnut orchard with secondary-treated wastewater. Though the projects were primarily designed to reduce wastewater discharge, both cities have gained from the water-supply benefits of applying reclaimed water. The mix of California crops and planting patters has been changing. These changes are the result of decisions made by large numbers of individuals, rather than the intentional actions by state policymakers. California farmers are planting more and more high-valued fruit and vegetable crops, which have lower water requirements than the field and grain crops they are replacing. They can also be irrigated with more accurate and efficient precision irrigation technologies. As a result, California is slowly increasing the water productivity of its agricultural sector, increasing the revenue or yield of crops per unit water consumed. Over time, these changes have the potential to dramatically change the face of California agriculture, making it even more productive and efficient than it is today, while saving vast quantities of water.

In the past two decades, California farmers have made considerable progress converting appropriate cropland and crops to water-efficient drip irrigation. Much of this effort has focused on orchard, vineyard, and berry crops. Recent innovative efforts now suggest that row crops not previously irrigated with drip systems can be successfully and economically converted. This case provides the example of two farmers converting bell peppers row crops to drip irrigation with great success. Subsurface drip irrigation substantially increased pepper yields, decreased water consumption, and provides greatly improved profits. Due to limited availability of public data, our research could only examine 50 of the top exporting commodities in California. According to the California Department of Food and Agriculture, there are 305 known crops produced in the region. Additional research should be extended to assess the exported water of the remaining 255 crops and to evaluate the overall effects of evapotranspiration for all crops commercially produced in California. Since many regions of California are classified as arid and semi-arid areas sharing similar climate conditions to those of other Mediterranean countries, such as Chile, Spain, France, Italy, South Africa and portions of Australia according to UNCCD. The information presented in our research model can be used as a baseline for reference for calculating exported water of other crops grown in similar climate conditions. Previous study by Nguyen et al., 2015 reported that groundwater pumping consumes approximately 1.5 x 104 GWh yr-1 , making the energy requirement for groundwater irrigation the largest contributor in the food production process. As shown from the results of our calculations, the majority of exported water was in the form of evapotranspiration induced by crop irrigation. Thus, it warrants that further research be conducted to examine the energy being exported as a result of induced evapotranspiration beyond the energy requires to irrigate. This research will shed light on the overall energy consumption in the entire food production process including energy expended within a spatial domain and the exported quantity induced via evapotranspiration. One area of research which has not been conducted is the effects of positive feedback mechanism of the overall exported energy of crops as a result of induced evapotranspiration. Future research should be extended to cover all remaining crops commercially produced in California. The outcomes of this model can be extended to quantify the overall exported energy from irrigation that is lost by induced evapotranspiration to that of the energy consumptions from other sectors of the California economy. The results of this future study will help close the loop on the life-cycle energy consumption analysis for California agriculture industry. Maximizing agricultural crop yield is an important goal for several reasons. First, a growing worldwide population will generate increased demand for agricultural resources. Since expanding the land area devoted to agriculture is often unfeasible, or would involve the destruction of sensitive landscapes such as forests and wetlands, the only way to meet this demand will be to increase the crop yield generated from existing farmland. Second, there are substantial economic incentives for profit-seeking farmers to maximize the yield of their crops, especially given the low profit margins typical of commercial agriculture.