By Jay Lund.
California is a big diverse place.
California probably will experience droughts this year of different types in different places, and no drought at all in some places, simultaneously. Even if conditions this year are very wet, with flooding, parts of California will have drought issues. (This is what makes California a great place to work on water problems.)
The first two months of this new water year have been wetter than average in the north and much drier than average in the south. But it is still early days.
Reservoir and Groundwater Storage Conditions
Reservoir storage in California is now about 2.5 million acre-feet below historical averages for this time of year. (This is 0.8 maf better than 2 months ago.) Some major reservoirs are below average, particularly Oroville, Trinity, San Luis, New Melones, and the Tulare Basin reservoirs. Cachuma Reservoir near Santa Barbara is in the worst shape at 7% of capacity or 10% of average storage for this time of year.
Groundwater will be recovering in northern parts of California, with less recovery in large parts of the southern Central Valley. (Can anyone suggest a set of online well elevation records in different parts of the Central Valley to create a groundwater storage index?)
October was a nice wet month, so soil moisture in much of the Sierras and Central California is improving, but remains in drought conditions (worsened by unusually high temperatures). Conditions for forests and native fishes remain depressed and will see drought impacts for years after hydrologic conditions improve.
This seemingly bad situation is substantially better than in this time a year ago. Something to be thankful for.
North of the Delta, so far we have above average precipitation and improving storage in most Sacramento Valley reservoirs. In the San Joaquin Valley, this water year’s precipitation is about average so far. But further south, the Tulare Basin has less than 50% of average precipitation so far this water year. And temperatures remain higher than average. So far, no snowpack – it is still a bit early.
Thoughts for the coming drought year
So far, overall drought conditions are mostly improving, but unevenly. We won’t really know how wet this year will be until late March. In October, this blog looked at overall drought conditions from several perspectives and statistical projections for the new water year. (This month’s election reminded us of the reliability and unreliability of statistical projections.)
Even if this year is wet, parts of California will experience drought or residual effects from five years of drought. The California Drought of 2017 will likely take several forms:
- Dry residential and community wells drought, affecting rural areas with lowered groundwater tables. Many of these household wells and small systems are in a precarious state even in wet years.
- Drought of surface irrigation water. Here surface water is unavailable and farmers mostly increase groundwater pumping, often at a higher cost and increasing regional groundwater depletion. This drought is more likely south of the Delta. Less surface being less available than irrigation demands south of the Delta is now a normal condition, due to a host of hydrologic, infrastructure, groundwater sustainability, economic and environmental factors, worsened by drought.
- Higher groundwater pumping cost drought. Even if this year is wet, many areas that pump groundwater will still face higher pumping costs for some years or longer from the drought’s cumulative groundwater depletions.
- Forest drought (including snow drought). Here, lack of soil moisture or its more rapid depletion with higher temperatures affects forest ecosystems.
- Ecosystem drought. Problems for some fish are likely to continue even if the year is wet, due to drought-depletion of some native fish populations. Dry conditions could also affect waterfowl. A drought of cold water in some reservoirs might affect both fish and farmers disrupted by reoperation of reservoirs.
- Urban drought. So far, most urban areas have pretty healthy water supplies. The big exception is Lake Cachuma in the Santa Barbara area, now at 10% of its long-term storage for this time of year.
- We could easily see some drought surprises. The wet season is still young. Welcome to California water, where anything can happen.
It is best to prepare for another drought year (and prepare for floods as well).
Here are some web sites to watch, mostly from the California Department of Water Resources’ fine California Data Exchange Center (CDEC) at http://cdec.water.ca.gov.