Suitable parcels for ag-MAR that can benefit community water supplies

• Disadvantaged Communities as defined by CA Proposition 84: a community with a median household income less than 80% of CA average.
  

Explanation

The Tulare Lake Basin is California’s most agriculturally intensive region, and unsustainable levels of groundwater extraction have an especially significant impact on the quantity and quality of water available for communities who rely on shallow groundwater wells for household consumption.

These communities have a complex relationship with the agricultural industry, relying on it for employment while experiencing detrimental effects on shared water resources. This study explores agricultural recharge (ag-MAR) as a tool to stabilize water supply for these communities that also benefits the agricultural industry.

Parcels displayed to the left (2,998 parcels, ~90,000 acres) are suitable ag-MAR locations that can help stabilize water supply in these communities.

Parcels Suitable for Ag-MAR

Explanation

Agricultural parcels determined suitable for ag-MAR must have appropriate soil drainage properties, crop tolerance to prolonged flooding, and availability of surface water for groundwater recharge.

In the Tulare Lake Basin, 9,758 agricultural parcels spanning almost 415,000 acres were identified as suitable for ag-MAR.

The figure below describes how the suitability of land parcels for agricultural recharge were determined.

Biophysical Indicators

Explanation of Indicators

Soil Suitability for Groundwater Recharge
Only parcels overlaying soil components rated as “Excellent”, “Moderate”, or “Good” were included.

Land Use/Land Cover
Only parcels with crops that tend to tolerate standing water well were included. These crop types were identified as pasture (e.g. alfalfa), idle lands, vineyards, grain and hay crops, and field crops (i.e. fallowed/cover-cropped in winter).

Surface Water Access
Ag-MAR projects require that surface water is accessible to apply to agricultural fields. Storm events in the region that require repeated flood flow releases can be captured by existing irrigation infrastructure and routed to agricultural fields, so the fields must be within a certain proximity of the infrastructure.

Citations

Soil Suitability for Groundwater Recharge (SAGBI)

Land Use/Land Cover (2014)

Surface Water Access

Disadvantaged Community Vulnerability to Groundwater Shortages

Explanation

Many disadvantaged communities (DACs) rely on shallow groundwater wells for all household use and have limited social and financial ability to cope with water shortages. The 2012-2016 drought compromised many of these wells, leaving many DACs without a reliable drinking water source. As extreme weather events are predicted to increase in number and severity, a portfolio of mitigation strategies must be developed to address the inherent and persistent vulnerability of these DACs.

DAC vulnerability is defined as the potential for a DAC to be at risk of a change in groundwater supply that diminishes access to clean, reliable drinking water due to social, economic, political, technological, institutional, and biophysical factors.

The figure below describes how vulnerability to groundwater shortages was determined.

Biophysical and Socioeconomic Indicators

Explanation of Indicators

Domestic Well Failures
In 2014, the Household Water Supply Shortage Reporting System was created to provide water systems serving one to fifteen households the opportunity to self-report water supply failures. 2,603 well failures were self-reported in California during the 2012-2016 drought period, of which 1,479 well failures occured within the study area.

Pesticide Applications (2015)
The California Department of Pesticide Regulation recognizes the following seven active ingredients contained in pesticides as a public health risk having the potential to pollute groundwater: atrazine, simazine, bromacil, diuron (except <7 percent diuron applied to foliage), prometon, bentazon, and norflurazon.

Land Subsidence (May 2015-Sept 2016)
Prolonged and unsustainable groundwater pumping continues to cause severe land subsidence throughout the study area. Land subsidence is the settling or sinking of the land surface due to subsurface movement of earth materials and can be caused by natural or human processes.

Connection Density (2014)
Communities that rely on a single water source are especially vulnerable to water supply shortages and contamination as the failure of a single source compromises the entire water supply. Additionally, communities where many people are connected to few water sources are also considered to be very vulnerable to water supply challenges as the failure of a single source compromises the water supply for a large population. This is a metric describing the number of active Public Water Supply System sources per water supply connections for each community.

Poverty Status (2015)
Poverty status in this study is defined as the percentage of the population for whom the ratio of income to national poverty level in the previous twelve months was below one.

Linguistic Isolation (2015)
Linguistic isolation in this study is defined as the percentage of households that are limited English-speaking households.

Educational Attainment (2015)
In this study educational attainment is defined as the percentage of population over 25 years of age who have completed some education above the high school level.

Metadata

Domestic Well Failures (2012-2016)

Pesticide Applications (2015)

Land Subsidence (May 2015-Sept 2016)

Connection Density (2014)

Socioeconomic Factors (2015)

References

Soil Suitability for Recharge (SAGBI)
O’Geen, A., Saal, M., Dahlke, H., Doll, D., Elkins, R., Fulton, A., … & Niederholzer, F. (2015). Soil suitability index identifies potential areas for groundwater banking on agricultural lands. California Agriculture, 69(2), 75-84.
©[2020] The Regents of the University of California.

Land Use/Land Cover (2014)
California Department of Water Resources. (2014). CADWR Land Use Viewer [Data file]. Retrieved from https://gis.water.ca.gov/app/CADWRLandUseViewer/

Surface Water Access
Direct communication with nine responsive agencies (Arvin Edison Water Storage District, Buena Vista Water Storage District, Fresno Irrigation District, Kern County Water Agency, Kern Delta Water District, Madera Irrigation District, North Kern Water Storage District, Tulare Irrigation District, Westlands Water District) and digitization from publicly available maps (e.g. groundwater management plans, integrated regional water management plans) and aerial images.

Domestic Well Failures (2012-2016)
California Department of Water Resources. (2019). Locally Reported Household Water Shortages for Drought Assistance [Data file]. Retrieved from personal communication.
Data Disclaimer: The State’s Household Water Supply Shortage Reporting System was established in late 2014 as a tool to capture information on water supplies running dry due to worsening drought conditions across California. The information gathered by the system was used for coordinating the State’s drought emergency response efforts. The system was set up as a voluntary, self-reporting system and, as such, only represents some fraction of the actual water supply shortages occurring. Most of the reported shortages were dry wells, but some were streams. While being self-reporting, most of the reports were actually received by county health officials who entered the data into the system. Some counties were very active in reporting, while some were not. The geographical data has a reduced latitude and longitude precision of one-hundredth of a degree to maintain personal information confidentiality. The reporting period for the dataset is through January 11, 2019.

Pesticide Applications (2015)
California Department of Pesticide Regulation. (2015). California Pesticide Information Portal [Data file]. Retrieved from https://calpip.cdpr.ca.gov/format.cfm

Land Subsidence (May 2015-Sept 2016)
NASA Jet Propulsion Laboratory. (2018). Total subsidence in the San Joaquin Valley for the period May 7, 2015 – Sept. 10, 2016 as measured by ESA’s Sentinel-1A and processed at JPL [Data file]. Retrieved from personal communication.

Connection Density; Disadvanataged Communities (2014)
Provost & Pritchard Consulting. (2014). Disadvantaged community locations in the Tulare Lake Basin [Data file]. Retrieved from personal communication.

Socioeconomic Factors (2015)
U.S. Census Bureau. (2015). TIGER/Line with Selected Demographic and Economic Data [Data file]. Retrieved from https://www.census.gov/geographies/mapping-files/time-series/geo/tiger-data.2015.html