We know that the Owens Valley plant communities that we monitor require periodic connection to the water table for long-term survival and recovery from drought. Through our monthly monitoring, we can easily detect the rise of water above the water table due to capillarity. The soil water and groundwater data show us which monitoring sites have plant root zones connected with the water table and which still need water table recovery. From these observations we can suggest possible reasons for vegetation conditions observed at a particular site and suggest appropriate pumping management.

Figure 2. Owens Valley permanent monitoring sites For simplicity, the wellfield monitoring sites are grouped into three categories to summarize the root zone/water table connection. The connection between the root zone and groundwater is not only related to water table depth. It also depends on the rooting depth of the vegetation and the soil characteristics. For example, in similar soils, a shallower water table is necessary to supply groundwater to grass-dominated sites than shrub-dominated sites because of the shallower roots of the grasses. Similarly, the capillary rise above the water table in a silty soil is much greater than in a sandy soil, allowing plants access to groundwater from greater depths. Brief descriptions of the three categories of root zone/groundwater connection are given below.

For management purposes, grass-dominated sites are assigned a root zone of 2 meters; shrub sites are assigned a 4-meter root zone.

• Disconnected: No groundwater is reaching the root zone. Six of the 33 monitoring sites occur in this category. Seven sites were disconnected last year.
• Weakly connected: Groundwater reaches the bottom 0.5 meters of the root zone. Six monitoring sites occur in this category. Nine sites were weakly connected last year.
• Connected: Groundwater extends to the middle of the root zone. Thirteen sites occur in this category. Nine sites were connected last year. All eight control sites located away from the effects of pumping also occur in this category.

  Relatively low pumping since 1990 and several high runoff years have promoted substantial water table and soil water recovery from the declines induced by heavy pumping at the onset of the 1987-1992 drought. As of April 1, 1999, the water table was supplying water to the root zone at 19 of the 25 monitoring sites located in wellfields (Figure 2). This compares to about six sites with groundwater in the root zone near the end of the drought in 1992. A few sites, particularly in Laws, Big Pine, and south of Independence, still need additional water table recovery to supply groundwater to the root zone. These areas experienced large water table declines due to pumping and thus had the farthest to recover. The water tables in areas outside the wellfields were not affected by pumping. The root zones at monitoring sites in these areas remained connected to the water table throughout the drought.

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