# Soil-Plant Water Balance and Groundwater

On-off according to Green Book Section III values for Vegetation Water Requirements

Water Department www.inyowater.org (County of Inyo)www.inyowater.org
2018-12-11

# Background

On/Off Well Management The Water Agreement and Green Book established procedures to determine which LADWP pumping wells can be operated based on soil water and vegetation measurements. As part of the monitoring effort for the Agreement, the Water Department regularly measures soil water content and vegetation leaf area index (with LADWP) to estimate vegetation water needs at 22 permanent sites located in wellfields and seven sites in control areas. Soil water monitoring is conducted monthly and vegetation monitoring is conducted annually in June. Each monitoring site is linked to one or more LADWP pumping wells. On July 1 and October 1, if the soil water is insufficient to meet the needs of the vegetation at a site, the linked pumping wells cannot be operated. The wells must remain off until the soil water exceeds the amount required by the vegetation at the time the wells went off. This is referred to as the On/Off management strategy. During much of the period since this management was implemented in 1990, LADWP has not operated numerous wells in On status in accordance with subsequent agreements with the County.

# Soil-Plant Water Balance and Groundwater

Data for each of the permanent monitoring sites (1990-present) is presented in three plots below with interactive features including zoom/pan and series/point highlighting. The first plot includes available water content (AWC) and vegetation water requirements (VWR) over time. The second plot includes the depth to water table (DTW) from the test well on the site. The third plot represents time periods when the site was either in on or off status over the management period.

The right margin contains further information: photo of the vegetation transect; which pumping wells are linked to the site; the most current on/off status; if in off status, the AWC required for well turn-on; and the identity of the associated test well.

Instructions

• Zoom out: Double click on a plot to zoom out to the full time series extent.
• Data point highlighting: Move cursor over the plot to display data values in the legend.
• Pan: Use slider range selector to display custom time periods.
• Zoom in: Drag horizontally to select time period or drag vertically to select a custom y-axis range.
• Grouped Selection: Selection in any plot will update all plots with this selection.