Almond Orchards Flooded in California to Restore Groundwater
Researchers from the University of California, Davis are studying whether almond orchards can be used to restore water to depleted aquifers. The excess water in the irrigation system from recent storms is being used to flood the farm of Nick Blom in Modesto to see if the aquifer that is 45 feet underground can be recharged to pre-drought levels.
Scientists at UC Davis are studying whether flooding almond orchards during the winter time can help pull California out of a chronic groundwater overdraft, at least in some areas. UC Davis hydrologist Helen Dahlke says soils have to be suitable for it – but researchers have mapped that out.
In order to increase water supply reliability new large-scale approaches need to be explored to actively recharge California’s groundwater aquifers at times when excess surface water is available. California’s Central Valley groundwater aquifers offer storage for approximately 50 million acre-feet of water that have been pumped over the past 70 years but could be replenished through establishment of local groundwater banks.
However, in order to achieve groundwater sustainability and to sustain California’s agricultural productivity and importance as one of the World’s leading food supplier California needs 1) to overcome legal, institutional and managerial impediments to groundwater recharge and (2) develop new technological approaches to recharge groundwater at larger scales. Irrigated agriculture covers approximately 9 million acres of land in California and utilizes approximately 80% of California’s water supply to produce food and fiber.
Because of the existing irrigation and water conveyance infrastructure that California’s irrigation agriculture provides large amounts of surface water could potentially be distributed onto agricultural fields during winter storms to recharge groundwater. However, knowledge gaps as to suitable locations, technical implementation and long-term operation remain. This project is aiming to close some of these knowledge gaps by assessing the physical, operational, economic and to some extent legal feasibility of agricultural groundwater banking (ag-GB) on agricultural land.
- Determine the most probable locations for ag-GB based on available soils, climatic, water supply and water infrastructure information using analysis tools such as GIS, and surface and groundwater modeling.
- Establish a knowledge database on the crop physiological performance of selected crops to flooding.
- Develop crop-specific and soil-landscape specific management guidelines and flooding suitability crop indices to assist stakeholders in mitigating the risk of yield loss due to ag-GB.
- Develop decision support tools for growers and stakeholders to estimate the on-farm costs and benefits of ag-GB.
The first step is a GIS analysis to find suitable ag-GB locations based on soil properties, available groundwater storage, land use, availability and connectedness to excess surface water and conveyance systems. This analysis is currently conducted for the entire Central Valley and will highlight where areas of concern with declining groundwater levels are meeting areas that have physical surface properties (e.g. conducive soils) to facilitate groundwater recharge.
In a next step we will conduct a water budget analysis for the most suitable sites to identify and quantify water supplies, water use, rainfall and groundwater use. This will provide input data for a hydro-economic model and a coupled surface water-groundwater model which we will use to simulate how much water could potentially recharge for a given parcel size and infiltration rate (e.g. 50 acre field). This model will also be used to estimate the time span that recharging water will take to reach the groundwater, how constituents are moved with the recharging groundwater, where the groundwater is moving and how much of the banked water can be recovered.