Why climate change reduces stormwater capture opportunities
by Grace Peng
September 2023
Hurricane Hilary was a test for stormwater systems throughout SoCal, but especially so in the inland deserts. It made national news when Interstate 10 was washed out and closed. I followed reports on social media, and that led me down a rabbit hole of learning how Palm Springs and other Coachella Valley cities were able to stabilize their groundwater basin through recharge investments.
I wrote a longer form article on my blog but it doesn’t mention the water transfer for water nerds. https://badmomgoodmom.blogspot.com/2023/08/when-too-much-water-leads-to-water.html
Palm Springs exists because of natural artesian wells that used to burst out of an aquifer that stored up water over geologic timescales. In just a few decades, white settlers, particularly farmers, drained the aquifer considerably. Valley residents and farmers realized that the 3” of average rainfall in the region could not recharge the aquifer naturally and that they would need to import water supplies. The Coachella Valley Water District (CVWD) website gives the history of the largely successful efforts.
http://www.cvwd.org/162/Groundwater-Replenishment-Imported-Water
In short, the CVWD and Desert Water Association (DWA) purchased water rights to the Colorado River Project (CRP) which supplies ⅔ of the water used by farmers in the valley. They also developed water recharge projects to direct rainfall and mountain runoff into percolation ponds. This stabilized the aquifer until the cities boomed & they needed additional water to keep up with the groundwater depletion.
CVWD & DWA purchased an additional 194,100 acre-feet/yr of State Water Project (SWP) water, making them the 3rd largest SWP rights holder. Since the Coachella Valley is already hooked up to the CRP, they swapped their SWP water with Metropolitan WD for the MWD’s CRP allocation. (1) However, SWP & CRP allocations are increasingly uncertain with climate change so they have been developing more groundwater recharge using natural flows where geology permits.
Groundwater recharge also becomes more difficult with climate change because storms are more intense and infrequent. Sediment-filled rain runoff had to be diverted from recharge areas during January storms (2) to prevent clogging them. Hurricane Hilary dumped 3 times the average annual rainfall for the Coachella Valley, and they (again!) couldn’t use it to replenish the aquifer. Recharge only works with sediment-free flows from light to moderate rains or imported water. The silver lining is that the recent heavy flows continued down the Whitewater River to the Salton Sea, eliminating the need (for now) to use CRP water to replenish it. (The Salton Sea exists because the fine silt underneath it is not conducive to percolation. Otherwise, it would be dry.)
Central Greece is experiencing a parallel double disaster where sediment-filled runoff poured off of mountainous forests (some recently burned), flooded farmland, and deposited fine silt and clay.(3) Three years worth of rain fell in 2 days (4), destroying ¼ of Greece’s farmland. Crops for not just this year, but for years to come, will be lost as farmers struggle to remove the clay.
September 2023
Hurricane Hilary was a test for stormwater systems throughout SoCal, but especially so in the inland deserts. It made national news when Interstate 10 was washed out and closed. I followed reports on social media, and that led me down a rabbit hole of learning how Palm Springs and other Coachella Valley cities were able to stabilize their groundwater basin through recharge investments.
I wrote a longer form article on my blog but it doesn’t mention the water transfer for water nerds. https://badmomgoodmom.blogspot.com/2023/08/when-too-much-water-leads-to-water.html
Palm Springs exists because of natural artesian wells that used to burst out of an aquifer that stored up water over geologic timescales. In just a few decades, white settlers, particularly farmers, drained the aquifer considerably. Valley residents and farmers realized that the 3” of average rainfall in the region could not recharge the aquifer naturally and that they would need to import water supplies. The Coachella Valley Water District (CVWD) website gives the history of the largely successful efforts.
http://www.cvwd.org/162/Groundwater-Replenishment-Imported-Water
In short, the CVWD and Desert Water Association (DWA) purchased water rights to the Colorado River Project (CRP) which supplies ⅔ of the water used by farmers in the valley. They also developed water recharge projects to direct rainfall and mountain runoff into percolation ponds. This stabilized the aquifer until the cities boomed & they needed additional water to keep up with the groundwater depletion.
CVWD & DWA purchased an additional 194,100 acre-feet/yr of State Water Project (SWP) water, making them the 3rd largest SWP rights holder. Since the Coachella Valley is already hooked up to the CRP, they swapped their SWP water with Metropolitan WD for the MWD’s CRP allocation. (1) However, SWP & CRP allocations are increasingly uncertain with climate change so they have been developing more groundwater recharge using natural flows where geology permits.
Groundwater recharge also becomes more difficult with climate change because storms are more intense and infrequent. Sediment-filled rain runoff had to be diverted from recharge areas during January storms (2) to prevent clogging them. Hurricane Hilary dumped 3 times the average annual rainfall for the Coachella Valley, and they (again!) couldn’t use it to replenish the aquifer. Recharge only works with sediment-free flows from light to moderate rains or imported water. The silver lining is that the recent heavy flows continued down the Whitewater River to the Salton Sea, eliminating the need (for now) to use CRP water to replenish it. (The Salton Sea exists because the fine silt underneath it is not conducive to percolation. Otherwise, it would be dry.)
Central Greece is experiencing a parallel double disaster where sediment-filled runoff poured off of mountainous forests (some recently burned), flooded farmland, and deposited fine silt and clay.(3) Three years worth of rain fell in 2 days (4), destroying ¼ of Greece’s farmland. Crops for not just this year, but for years to come, will be lost as farmers struggle to remove the clay.
July 2023
As I explained in my presentation in September 2022, How to move water from the Mississippi River to California the low energy way, SoCal is one of the regions outside the natural Colorado River Basin (CRB), but dependent on CRB water. 40 M Americans depend on the over-allocated Colorado River (CR), but some regions are in better legal and physical (infrastructure) position than others.
Today, I’m reporting on the headwater state, Colorado. According to Water Education Colorado, the CR crisis would dry out the Front Range cities on the eastern side of the continental divide. 4 M of Colorado’s 5 M population live along the Front Range. Half of the water used on the Front Range currently comes from the CR. The infrastructure to move CR water from the Western Slope, across the continental divide, to the Front Range communities of Ft Collins-Boulder-Denver-CO Springs-Pueblo (and many smaller cities and farms/ranches) were developed relatively late.
Under the Right of Prior Appropriation, 97% of Front Range CR water is junior to senior rights holders such as SoCal’s Metropolitan Water. This means, even though my home in Boulder, CO is < 15 miles from the headwaters of the CR, my home in Redondo Beach, CA will be served first with CR water.
Senior water rights holders get water first. Junior rights holders only get served if there is sufficient water left over. The CR was overallocated (15 MAF/year) while recent flows have averaged 12 MAF/year. With Climate Change, the air, soil and vegetation will be thirstier, further reducing surface river flows to the point that junior water CR rights holders are not expected to receive any water in typical years.
The future need not be grim, if Coloradans were to conserve. Denver residents currently use twice as much water per capita as Angelenos. If they were to conserve, recycle, and capture more rainwater, they have a chance to head off disaster. But, many would prefer to blame Californians for stealing “their water”.
______________________________________________________________________
(1) http://www.cvwd.org/162/Groundwater-Replenishment-Imported-Water
(2 https://kesq.com/news/2023/01/13/coachella-valley-water-district-clarifies-plan-to-redirect-storm-runoff-from-percolation-ponds/
(3) https://www.cbsnews.com/news/greece-flooding-deaths-rescues-turkey-bulgaria-climate-change-severe-weather/
(4) https://reliefweb.int/map/greece/greece-recent-floods-and-wildfires-dg-echo-daily-map-06092023
As I explained in my presentation in September 2022, How to move water from the Mississippi River to California the low energy way, SoCal is one of the regions outside the natural Colorado River Basin (CRB), but dependent on CRB water. 40 M Americans depend on the over-allocated Colorado River (CR), but some regions are in better legal and physical (infrastructure) position than others.
Today, I’m reporting on the headwater state, Colorado. According to Water Education Colorado, the CR crisis would dry out the Front Range cities on the eastern side of the continental divide. 4 M of Colorado’s 5 M population live along the Front Range. Half of the water used on the Front Range currently comes from the CR. The infrastructure to move CR water from the Western Slope, across the continental divide, to the Front Range communities of Ft Collins-Boulder-Denver-CO Springs-Pueblo (and many smaller cities and farms/ranches) were developed relatively late.
Under the Right of Prior Appropriation, 97% of Front Range CR water is junior to senior rights holders such as SoCal’s Metropolitan Water. This means, even though my home in Boulder, CO is < 15 miles from the headwaters of the CR, my home in Redondo Beach, CA will be served first with CR water.
Senior water rights holders get water first. Junior rights holders only get served if there is sufficient water left over. The CR was overallocated (15 MAF/year) while recent flows have averaged 12 MAF/year. With Climate Change, the air, soil and vegetation will be thirstier, further reducing surface river flows to the point that junior water CR rights holders are not expected to receive any water in typical years.
The future need not be grim, if Coloradans were to conserve. Denver residents currently use twice as much water per capita as Angelenos. If they were to conserve, recycle, and capture more rainwater, they have a chance to head off disaster. But, many would prefer to blame Californians for stealing “their water”.
______________________________________________________________________
(1) http://www.cvwd.org/162/Groundwater-Replenishment-Imported-Water
(2 https://kesq.com/news/2023/01/13/coachella-valley-water-district-clarifies-plan-to-redirect-storm-runoff-from-percolation-ponds/
(3) https://www.cbsnews.com/news/greece-flooding-deaths-rescues-turkey-bulgaria-climate-change-severe-weather/
(4) https://reliefweb.int/map/greece/greece-recent-floods-and-wildfires-dg-echo-daily-map-06092023