science delivers an answer on Great Lakes water levels

Shame on me for repeating news from reporters without looking into the numbers in greater detail.  I’m not terribly surprised to find out that a swath of recent research on the dynamics of climate, ice cover, evaporation, and flow rates in the Great Lakes system has been published.  There’s a great article chock full of details and solid explanations of the research here on the National Geographic Water Currents blog.  Here’s the take-home message, which should settle the debate on why water levels are so low in the Great Lakes:

Lake water levels are heavily influenced by the amount of ice cover in the winter.  Ice cover in the winter affects when and how much the lake evaporates in the summer.  Ice cover has been at record lows, with a singularity in the winter of 1997-1998.  Since then, significant evaporation has started earlier in the summer, and the lake water has been getting steadily warmer.  This means that the annual onset of water level declines is starting earlier in the year, too, which all leads to lower average water levels.

The scientists apparently don’t want to speculate on the influence of climate change, since water levels aren’t yet statistically different from historical ranges.  Fine, but increasing surface temperature and decreasing ice cover/snowpack are two clear factors in favor of this explanation.  I suspect that the drought is the short-term driver of losses in the Great Lakes system, but climate change is the long-term driver, perhaps of both the Great Lakes system and the drought itself.

Happy Thanksgiving to all — let us be thankful for what we have to drink!

canary in the coal mine

[*Note: Sorry I didn’t get this post up on Monday.  Things got away from me, being out of town this weekend for fun and then all day Monday for work.  We should be back on track for the rest of the week.*]

People like to talk about water issues in the West like they’re a special case. And by and large, they’re right — water scarcity in the Southwestern US brings up issues of water rights and alternate supplies well before they hit the rest of the country. But the rest of the country is not immune to water scarcity, despite the relative abundance of rainfall (San Diego: 10 inches per year; Boston: 42.5 inches per year; Atlanta: 50.2 inches per year). Really provocative thinkers propose grand schemes to save the West like piping water from the Great Lakes to the Colorado River. Well, besides a large number of Michiganders, Chicagoans, Wisconsinites and others who would insist that the West can’t have their water, things aren’t perfectly rosy in the Great Lakes.

In fact, Lake Michigan recently hit its record low. What happened? Lake levels vary quite a bit (a few feet) annually, but Lakes Michigan and Superior have been below the long-term average since the late 1990s.  Their main outflow, the St. Clair River, has been heavily dredged, which increases the rate water exits the lake basins.  Add in a touch of climate change (you may have heard of the spectacular drought across the US this year), and there’s just not as much water in the system.

I don’t know what the answer is here, but it is worth pointing out that water mismanagement–or perhaps, lack of management–is a nationwide issue.  The impacts may hit the Southwest first, but the story of water scarcity across this country is not going away any time soon.

planning is for squares

I promised an assessment of the Hetch Hetchy reservoir inflows, outflows, and storage, and I intend to deliver something.  I looked into the reservoir, from the data available from USGS to the Restore Hetch Hetchy website to the San Francisco Public Utility Commission’s official position on Proposition F to the California Department of Water Resources (DWR) 2006 study on restoration of the Hetch Hetchy valley.  There are many things out there with opinions, but I intend to highlight the facts.

  1. Storage, inflows, and outflows.  The Hetch Hetchy reservoir has stored an average of 282,100 acre-feet over the past 5 years, with an extreme maximum storage of 363,300 acre-feet and a minimum storage of 154,200 acre-feet.  I can see a couple of jumps in the plots of storage vs. time that suggest the dam is occasionally operated to send water to other locations, so a true picture of the storage in the system would need to include all 8 reservoirs in the system and river flow at multiple locations.  Honestly I don’t have time to get to this.  But I can say that in the past 5 years, the SF utility system has used at least 363,000 – 154,200 = 209,100 acre-feet stored in the Hetch Hetchy reservoir.  The other 7 dams owned by the San Francisco Public Utility Commission (SFPUC) have a combined storage of 537,600 acre-feet [Urban Water Management Plan, 2010].  So just to store the water that was stored in Hetch Hetchy and used in the past 5 years, you would need to use approximately 40% of the remaining reservoir space in the entire 7-dam network, and it’s not like those reservoirs are normally sitting empty.
  2. Water storage needs.  The Restore Hetch Hetchy plan calls for water intake via pipes without the dam.  The storage can be maintained by the rest of the reservoirs on the system.  “Hydrologic analysis shows that it will be possible to fully meet system demands in 4 out of 5 years. In the driest years, 20% of system demands will need to be met from additional water storage or supply resources.”  This is a direct quote from the Restore Hetch Hetchy website.  Let’s examine this.  One in every five years, this new Hetch-Hetchy-free system would experience a water shortage.  Have you ever heard of a utility plan to have water shortages?  We have utilities to provide reliability, and even then 20-year, 50-year, and 100-year events can overwhelm the infrastructure we have.  A 20-year event is a disaster, rather than an inconvenience, when your planning basis is a 5-year event.  Civil engineers like to design for 20-year events, at a bare minimum, with floods like the 1993 Mississippi River flood or the 2005 Hurricane Katrina disaster bringing calls for 500-year and 1000-year designs for water management (in those cases, we’re talking levees rather than dams, but droughts can be equally devastating).
  3. New supplies. The second half of the above quote addresses where additional water supplies will come from in the dry years: “additional water storage or supply resources.”  Let me refresh your memory, San Francisco — California’s water supply is already overallocated.  I just drove down I-5 this weekend and saw farmers’ billboards complaining about “Congress-created dust bowl” with cuts in water supply listed.  Those weren’t Congress-created cuts, those were drought-created cuts combined with a federal judge upholding the primacy of the Endangered Species Act, specifically related to fish in the Bay-Delta, over California’s water allocations.  There isn’t enough water for everything we already want to do.  Please, Restore Hetch Hetchy, tell us where the water will come from.  Water storage measures and water recycling facilities take time, money, and planning, and can’t happen overnight once the dam removal is underway.
  4. Climate change.  Finally, I will just note that climate change is projected to decrease snowpack (nature’s water storage) in the Sierras and increase the frequency and duration of “extreme” events, both rainfall and drought.  To remove excess storage from the water supply system in light of this very real challenge to California’s water supplies is very short-sighted.

That’s enough for now about water flows.  Next time, I’ll tell you what the DWR’s own report recommended for the Hetch Hetchy restoration question.  Hint: it’s not what’s in Proposition F.

taking things into one’s hands

The New York Times, among others, is reporting that a private entrepreneur dumped 100 tons of iron dust off the shore of western Canada this summer, in an attempt to influence the local climate.  The idea goes that iron stimulates growth of plankton, who take up carbon dioxide locally, and then die and sink to the bottom of the ocean — carbon trapped!  Planet saved!  Well, things aren’t quite that simple.

Certain swaths of the ocean are ripe for plankton growth, just limited by trace nutrients.  In fact, if you add iron to these parts of the ocean, you can get a large bloom of phytoplankton in the shallow ocean, and they do take up a lot of carbon dioxide locally.  Then they die and are eaten by other microorganisms (the bigger microorganisms eat the littler ones — just like fish), who re-emit carbon dioxide and methane, another greenhouse gas.  That sort of negates the effect of the phytoplankton at the surface.  The trick is, iron fertilization only works to sequester carbon if you can get it to settle out to the bottom of the ocean, which is rather deep.  Like 4,000 meters / 12,000 feet deep.  It’s really hard to get biomass to sink past ~200 meters.  In the natural cycle of things, only roughly 20-30% of the biomass in the shallow ocean makes it to the deep ocean.

Actual iron fertilization experiments have had very mixed results, with most of them showing evidence of more rapid biomass cycling in the shallow ocean, but little evidence for significant burial at depth.  The response also depends strongly on the specific location that is fertilized (all parts of the ocean are not the same).

So this entrepreneur got tired of the wishy-washiness of scientists and politicians, and took matters into his own hands, apparently at the invitation of a native American population that wanted to stimulate their salmon population.  He would like to start a company to dump iron in the ocean to get carbon credits from emissions trading schemes, but if the carbon isn’t actually buried in the deep sea, he shouldn’t be getting any carbon credits (= money) for his work!  Plus, in light of the mixed results of the science, politicians decided not to allow any further experimentation under ocean dumping agreements — the London Convention and the UN Convention on Biological Diversity.

I don’t know what the results will show, as far as the fish are concerned, but to conduct “experiments” on this scale is reckless and sets a dangerous precedent.  What if some rogue decides to “geoengineer” the climate based on pseudo-science and causes a massive disaster?  There’s a reason why geoengineering hasn’t been adopted yet — it hasn’t been proven yet on a pilot-scale!  Aerosols like sulfate will cause acid rain, iron might just cycle carbon faster in the shallow ocean without any long-term burial, and carbon capture and sequestration may leak significantly…When science finds that silver bullet for climate change, we will let you know.

the answer is beneath your feet

California is facing some worrisome pressures from increasing water demand for a growing population and decreasing supply reliability due to climate change and environmental pressures on the Bay-Delta region.  What should California do, when faced with extreme drought?  A new study released by the California Energy Commission recommends creating and maintaining a water storage bank underground.  That is, California should store excess water underground, and then pump it out as needed when extreme drought arrives.  I’ve been a fan of this idea (“Managed Aquifer Recharge” or “Managed Underground Storage” are two broad names for the idea) since I first heard about it some 6 years ago in grad school, and it’s great to see that policy advisers and think-tanks are starting to come around.  If we can educate the rest of California, including politicians, then we might actually have a shot at making things happen.