A Soil Agricultural Groundwater Banking Index for California

By: Toby O’Geen Soil Resource Specialist in Cooperative Extension Dept. of Land, Air and Water Resources, UC Davis

Team members: Helen Dahlke, David Doll, Rachel Elkins, Graham Fogg, Alan Fulton, Thomas Harter, Jan Hopmans, Chuck Ingles, Franz Niederholzer, Matt Saal, Sam Sandoval, Larry Schwankl, Paul Verdegaal, and Mike Walkinshaw Can we capture and infiltrate water on agricultural lands during times of excess? Which Soils Work Best?

Coarse textured & Claypans Layered soils Homogeneous Other Considerations:

Root zone residence time: Crops and management are adversely affected by saturation.

Topography: Slopes that negatively influence the even distribution of water.

Chemical Limitations: High soil salinity may degrade groundwater quality.

Soil surface condition: some soils are susceptible to compaction and erosion if large volumes of water are applied. Model Development using SSURGO Data SAGBI SAGBI modified for rating deep tillage

Deep Root zone Topographic Chemical Surface Percolation residence time limitations Limitations Condition

Lowest Ksat Harmonic Slope class Electrical Erodibility Restrictive mean ksat SSURGO Conductivity Factor Kw layers drainage

Fuzzy logic: Fuzzy logic: Crisp ratings Fuzzy logic: Fuzzy logic: more is better more is better less is better less is better Fuzzy Logic Rating System Optimum & less is better More is better 1 1 rating rating

Fuzzy 0 Fuzzy 0 0 EC 50 060Ksat Rating Spatial Extent of SAGBI Factors

A. Deep percolation B. Root zone residence C. Salinity D. Surface condition SAGBI NOT Accounting for Deep Tillage

5.1 million acres suitable for groundwater banking Claypans and Hardpans Modified by Deep Tillage

Many soils that contain restrictive horizons have been modified by deep tillage. Land Cover in the Tulare Lake Basin What are the suitable cropping systems? extent and vulnerability SAGBI Accounting for Deep Tillage

Gained 518,879 acres of suitable land Interactive Map & Index Transparency http://casoilresource.lawr.ucdavis.edu/soilweb /

Surface Chemical Root zone Deep Slope condition limitations residence percolation Poor (0.45) Good Moderate Poor Good (2 dsm‐1) (ksat = 2 µms‐1) (ksat = (1 %) 0.1 µms‐1) 0‐No tolerance for standing water Vine & Tree Crop 1‐Tolerant of standing water up to 48 hours 2‐Tolerant of standing water up to 1 week Tolerance to 3‐Tolerant of standing water up to 2 weeks Saturation 4‐Tolerant of standing water > 2 weeks Crop Rootstock Tolerance Tolerance after before bud break bud break Peach; peach x almond 11 Almonds hybrid Almonds Plum; peach x plum hybrid 2 ‐34 Avocados Seedling, clonal 0 0 Cheries ‐ ?? Citrus ‐ 00 Wine Grapes ‐ 4* 2* Pears P. betulaefolia 4 4 Pears P. communis 4 3 Pears Cydonia oblonga (quince) 3‐42‐3 Pistachios ‐ ?? Plums/prunes Peach 1 1 Plums/prunes Plum; peach x plum hybrid 2‐31 Walnuts 2‐31 What does Agricultural Groundwater Banking Look Like?

How much is too much or too often?

http://www.npr.org Future Questions:

• What are the most appropriate crops for GW banking? • What about the potential for contamination? • How can we address concerns of growers? • What types of grower incentives might be available and how can they be cultivated? • What are the other existing barriers to this practice?