Tuesday, February 17, 2009

Hydropower in California

Yesterday I began by commenting on the NYT article on the need for coal-fired power plants, which led me to the discovery that California still gets over 32% of its power from coal with the next largest supply source being natural gas at 31% (it has dropped between 2005 and 2007 from 33%, just as coal has dropped from 38%). Eligible renewables had grown in that period from 5% to 12%, and hydro had stayed the same at 24%. The largest growth had been the increase in small hydroelectric power from 1 – 6%. (Wind is at 2% and solar <1%) With hydro now adding up to 30% of California power, and with Dr Chu commenting a couple of weeks ago about California water shortages:
Chu warned of water shortages plaguing the West and Upper Midwest and particularly dire consequences for California, his home state, the nation's leading agricultural producer.

In a worst case, Chu said, up to 90% of the Sierra snowpack could disappear, all but eliminating a natural storage system for water vital to agriculture.
It seemed time to see where all the hydro stations are that supply California, and see if they are in similar trouble to agriculture.

The first thing I discovered is that the numbers in the first paragraph are, if not wrong, somewhat misleading. At least according to the California Energy Commission. They show that Natural gas provides 45.2% of the electric power, nuclear 14.8%; Large hydro 11.7%; coal 16.6% and renewables 11.8%. And of the renewables small hydro provides 2.8%, for a total input to the state of 14.6% for hydro. What is further interesting is that of the coal power that produces 16.6% of the state’s energy only 2% is produced in state, and the rest is imported. Solar however still only produces 0.2% of state need, and wind 2.3%, most of that internal to the state.

The state itself produces around 69.5% of the electricity that it uses. I’ll leave it for another day to discover where the earlier numbers come from. What I would like to focus on is the hydro-electric part.
In 2007, hydro-produced electricity used by California totaled nearly 43,625 gigawatt-hours (GWh) or 14.5 percent of the state's total system power. In-state production accounted for 69.5% of all hydroelectricity, while imports from other states totaled 30.5%.A total of 343 hydroelectric facilities are in California with an installed capacity of 13,057 megawatts (MW). Hydro facilities are broken down into two categories: larger than 30 MW capacity are called "large hydro"; smaller than 30 MW capacity is considered "small hydro" and are totalled into the renewable energy portfolio standards. The amount of hydroelectricity produced varies each year. It is largely dependent on rainfall.

Power plants in California (note the blue hydro ones)

In a good year (such as 1983) the state can get up to 59,350 GWh of power from hydro. But in a bad year the amount can fall significantly.
(Source CA Energy Commission)
Note there is a difference between the CA production 27,000 GWh, and the overall hydro total of 43,000 GWh.

The water outlook for the state is not good,
As of February 1, 2009, statewide hydrologic conditions were as follows: precipitation, 65 percent of average to date; runoff, 35 percent of average to date; and reservoir storage, 65 percent of average for the date. . . . . For California statewide, January 2009 was the eighth driest January on record, with precipitation at about 30 percent of average for the month. In general, temperatures were significantly above average. On February 1, 2009, the Northern Sierra 8-station Precipitation Index had accumulated a seasonal total of 17.7 inches, which is 66% of the seasonal average to date and 35% of an average Water Year (50.0 inches). During January 2009, the 8-Station Index received only 3.1 inches, about 34% of average. Last year at this time, the 8-Station Index had 25.1 inches for the seasonal total.

The historic snowpack can be put in context with the drought scenario above:
(Source CA Water )

The current prediction for drought in the region from NOAA is that the drought will persist through at least April. And from the drought monitor:
Moderate to heavy precipitation (over 1 inch) was widespread across the southern Cascades, the Sierra Nevada, the coastal regions of California, and the southwestern California mountains, with amounts of 3 to 6 inches fairly common in southwestern California. However, since this was the first substantial precipitation across the state in several weeks, and because reservoir levels remain low and higher-elevation snowpack is still considerably below normal, drought classification improvements were limited. Specifically, moderate drought was re-classified as abnormal dryness through most of the climatologically arid areas in southeastern California and in southern Nevada while D0 conditions retracted westward out of west-central and southwestern Arizona. For the state of California as a whole, combined reservoir storage has dropped to levels typically observed only once every 10 to 20 years in February, and some areas reliant on relatively small-scale water supply systems are bracing for mandatory water usage cutbacks for the coming spring and summer.

In short hydropower may be a little short this summer, and the question will then be where they turn to get the additional supply. It will be interesting to see.

And since there is a virtually real-time counter and graph available, we will be able to do that. As I noted yesterday, however, you shouldn't start to get concerned until the projected numbers start getting over 50,000 Megawatts.


  1. Pleased to find this blog when I followed a link from TOD. I read there less now than before, commenting (as porsena) very rarely these days. However, I wanted to say your TOD posts on the technical background for energy sources have been very helpful to this outsider.

    The depressed water outlook for California seems part of a large scale weather pattern. Last week in southwestern British Columbia, the mountain snowpack was roughly 50-60% of normal, at a time when about three-quarters of the annual snowpack should have formed. In Victoria, where I live, the precipitation so far in 2009 is 58% of normal.

    About 92% of BC's electricity needs come from hydro. In a good water year, BC is a net exporter of electricity, mostly to Washington and Oregon but also to California. In poor water years, BC is a net electricity importer. Despite growth in the wind sector, it seems likely that California and BC will rely on fossil fuels for more electric power than normal this year. I don't, though, know how the economy is affecting the demand for electricity.

    While this winter has been unusually dry, the longer term trend in snowpack accumulation has been strongly downwards in southern BC since 1956, consistent with the effects of winter warming. The Canadian Regional Climate Model confirms a winter drying trend through the middle of this century in southern BC and western Washington, suggesting that hydro power will become increasingly less important.

  2. Most renewable sources of energy, hydro being but one, provide a varying source of power. The problems come when demand rises and, at the same time, one source or another (wind, solar, hydro, natural gas) is not available. What is the backup plan? Bear in mind that the consequences differ depending on where in the country you are when this happens.
    I suspect we are all going to learn a fair bit about this in the next few years.