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1. Water shortage risks from perennial crop expansion in California’s Central Valley

   https://doi.org/10.1088/1748-9326/ab4035  

   Mall, Natalie K. ; Herman, Jonathan D. ( October 2019 , Environmental Research Letters)

   California’s Central Valley is one of the world’s most productive agricultural regions. Its high-value fruit, vegetable, and nut crops rely on surface water imports from a vast network of reservoirs and canals as well as groundwater, which has been substantially overdrafted to support irrigation. The region has undergone a shift to perennial (tree and vine) crops in recent decades, which has increased water demand amid a series of severe droughts and emerging regulations on groundwater pumping. This study quantifies the expansion of perennial crops in the Tulare Lake Basin, the southern region of the Central Valley with limited natural water availability. A gridded crop type dataset is compiled on a 1 mi²spatial resolution from a historical database of pesticide permits over the period 1974–2016 and validated against aggregated county-level data. This spatial dataset is then analyzed by irrigation district, the primary spatial scale at which surface water supplies are determined, to identify trends in planting decisions and agricultural water demand over time. Perennial crop acreage has nearly tripled over this period, and currently accounts for roughly 60% of planted area and 80% of annual revenue. These trends show little relationship with water availability and have been driven primarily bymore »market demand. From this data, we focus on the increasing minimum irrigation needs each year to sustain perennial crops. Results indicate that under a range of plausible future regulations on groundwater pumping ranging from 10% to 50%, water supplies may fail to consistently meet demands, increasing losses by up to 30% of annual revenues. More broadly, the datasets developed in this work will support the development of dynamic models of the integrated water-agriculture system under uncertain climate and regulatory changes to understand the combined impacts of water supply shortages and intensifying irrigation demand.

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2. Use of alternative water sources in irrigation: potential scales, costs, and environmental impacts in California

   https://doi.org/10.1088/2515-7620/ab915e  

   Qin, Yuwei ; Horvath, Arpad ( May 2020 , Environmental Research Communications)

   Under the risk of drought, unreliable water supplies, and growing water demand, there is a growing need worldwide to explore alternative water sources to meet the demand for irrigation in agriculture and other outdoor activities. This paper estimates stocks, production capacities, economic costs, energy implications, and greenhouse gas (GHG) emissions associated with recycled water, desalinated brackish and seawater, and stormwater in California, the largest US state and the most significant fresh and processed food producer. The combined recycled water and stormwater supply could increase the share of alternative water use in urban land irrigation (parks and golf courses) from the current rate of 4.6% to 48% and in agriculture from 0.82% to 5.4% while increasing annual water costs by $900 million (1.8% of California’s annual agricultural revenue) and energy use by 710 GWh (0.28% of California’s annual electricity consumption). The annual supply of alternative water greatly exceeds the amount of water currently used in the food processing industry. In case studies of high-value agricultural produce, conventional water use was found to contribute approximately 17%, 12%, 4.1%, and 1.7% to the total GHG emissions of avocados, lemons, celery, and strawberries, respectively. However, materials (mostly packaging) contribute 46%, 26%, 47%, andmore »66%, and diesel use on farms 18%, 28%, and 14% for lemons, celery, and strawberries, respectively (data for avocados were not available). Switching to recycled water or stormwater would increase the total GHG emissions of one serving size of packaged strawberries, celery, lemons, and avocados by 3.0%, 7.8%, 11%, and 27%, respectively, desalinated brackish water by 23%, 58%, 150%, and 210%, and desalinated seawater by 35%, 88%, 230%, and 320%. Though switching to alternative water will increase costs, energy demand, and GHG emissions, they could be offset by turning to less environmentally damaging materials in agricultural production and sales (especially packaging).

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3. Agricultural Water Governance in the Desert: Shifting Risks in Central Arizona

   York, Abigail M ; Eakin, Hallie ; Bausch, Julia C ; Smith-Heisters, Skaidra ; Anderies, John M ; Aggarwal, Rimjhim ; Leonard, Bryan ; Wright, Katherine ( June 2020 , Water alternatives)

   In Arizona, the policy debates over the Colorado River Basin Drought Contingency Plans exposed long-running tensions surrounding how we use and value scarce water resources in a desert. These negotiations also highlighted generations-old disputes between indigenous communities’ water rights and Anglo settlers. This paper explores how irrigators respond to, and participate in, the crafting of institutional arrangements while at the same time experiencing increased exposure to climatic and hydrological risk. Our analysis incorporates qualitative interview data, a literature review, archival information from policy reports, and secondary data on water use and agricultural production. Building on the fieldwork with farmers and water experts that we completed before the drought contingency planning efforts began, we describe the status quo and then explore potential future contexts based on shifting incentives and on the constraints that arise during periods of Colorado River water shortages. Through an understanding of the socio-hydrological system, we examine the region’s agricultural water use, water governance, indigenous water rights and co-governance, and the potential future of agriculture in the region. Our study illustrates how the historic and current institutions have been maintaining agricultural vibrancy but also creating new risks associated with increased dependence on the Colorado River.
4. An Efficient, Memory-Saving Approach for the Loewner Framework

   https://doi.org/10.1007/s10915-022-01800-3  

   Palitta, Davide ; Lefteriu, Sanda ( March 2022 , Journal of Scientific Computing)

   The Loewner framework is one of the most successful data-driven model order reduction techniques. IfNis the cardinality of a given data set, the so-called Loewner and shifted Loewner matrices$${\mathbb {L}}\in {\mathbb {C}}^{N\times N}$$$L\in C^{N\times N}$and$${\mathbb {S}}\in {\mathbb {C}}^{N\times N}$$$S\in C^{N\times N}$can be defined by solely relying on information encoded in the considered data set and they play a crucial role in the computation of the sought rational model approximation.In particular, the singular value decomposition of a linear combination of$${\mathbb {S}}$$$S$and$${\mathbb {L}}$$$L$provides the tools needed to construct accurate models which fulfill important approximation properties with respect to the original data set. However, for highly-sampled data sets, the dense nature of$${\mathbb {L}}$$$L$and$${\mathbb {S}}$$$S$leads to numerical difficulties, namely the failure to allocate these matrices in certain memory-limited environments or excessive computational costs. Even though they do not possess any sparsity pattern, the Loewner and shifted Loewner matrices are extremely structured and, in this paper, we show how to fully exploit their Cauchy-like structure to reduce the cost of computing accurate rational models while avoiding the explicit allocation of$${\mathbb {L}}$$$L$and$${\mathbb {S}}$$$S$. In particular, the use of thehierarchically semiseparableformat allows us to remarkably lower both the computational cost and the memory requirements of the Loewner framework obtaining amore »novel scheme whose costs scale with$$N \log N$$$NlogN$.

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5. Micro-climate to macro-risk: mapping fine scale differences in mosquito-borne disease risk using remote sensing

   https://doi.org/10.1088/1748-9326/ac3589  

   Boser, Anna ; Sousa, Daniel ; Larsen, Ashley ; MacDonald, Andrew ( November 2021 , Environmental Research Letters)

   Mosquito-borne diseases (MBD) threaten over 80% of the world’s population, and are increasing in intensity and shifting in geographical range with land use and climate change. Mitigation hinges on understanding disease-specific risk profiles, but current risk maps are severely limited in spatial resolution. One important determinant of MBD risk is temperature, and though the relationships between temperature and risk have been extensively studied, maps are often created using sparse data that fail to capture microclimatic conditions. Here, we leverage high resolution land surface temperature (LST) measurements, in conjunction with established relationships between air temperature and MBD risk factors like mosquito biting rate and transmission probability, to produce fine resolution (70 m) maps of MBD risk components. We focus our case study on West Nile virus (WNV) in the San Joaquin Valley of California, where temperatures vary widely across the day and the diverse agricultural/urban landscape. We first use field measurements to establish a relationship between LST and air temperature, and apply it to Ecosystem Spaceborne Thermal Radiometer Experiment data (2018–2020) in peak WNV transmission months (June–September). We then use the previously derived equations to estimate spatially explicit mosquito biting and WNV transmission rates. We use these maps to uncovermore »significant differences in risk across land cover types, and identify the times of day which contribute to high risk for different land covers. Additionally, we evaluate the value of high resolution spatial and temporal data in avoiding biased risk estimates due to Jensen’s inequality, and find that using aggregate data leads to significant biases of up to 40.5% in the possible range of risk values. Through this analysis, we show that the synergy between novel remote sensing technology and fundamental principles of disease ecology can unlock new insights into the spatio-temporal dynamics of MBDs.

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