Listen here on Spotify | Listen here on Apple Podcast
Episode released on September 19, 2024
Episode recorded on June 13, 2024
Brian Richter is the President of Sustainable Waters, a global organization promoting solutions in a time of scarcity.
Highlights | Transcript
Recent paper titled “New Water accounting Reveals why the Colorado River no longer reaches the Sea in Communications Earth & Environment provides comprehensive accounting of the Colorado River that is essential for developing approaches to managing water use.
Results for Colorado River indicate that average consumptive water use (2000 -2019) includes 52% for agriculture, 19% for riparian & wetland evapotranspiration, 18% municipal/commercial/industrial, and 11% for reservoir evaporation (Fig. 1) (Richter and others, Nature Comm, 2024). A new aspect was including water use by natural vegetation. This study shows water intensity of alfalfa and grass hay (~62% of irrigation water use).
Previous study in Nature Water indicated that alfalfa hay was the dominant water consumer in 57% of water subbasins in the Western US, accounting for about a third of the water use (Fig. 2). Production of alfalfa has been increasing. However, the study highlights how changing crop mixes and fallowing could reduce water consumption by ~28 – 57%.
Analysis indicates that beef production has remained fairly stable but dairy production has been increasing, highlighting the water intensity of yogurt and cheese production.
Would be good to have long-term water planning in the Colorado River similar to what Texas uses (50 yr planning) rather than reactive planning year by year.
Brian Richter also found that population growth and water use are being decoupled in cities in the Colorado River Basin with 28% increase in population and 18% reduction in water use in 28 utilities (population served, 23 million) (Richter, J Water Resour. Plan. & Manag., 2023). This reduction in water use is mainly related to decreased outdoor water use (xeriscaping, native vegetation, financial incentives etc).
There is increasing interest in transferring water from rural to urban areas. Brian Richters hometown of San Diego developed an agreement with Imperial Irrigation District (IID) for Colorado River water (~ 40% of San Diego water use) in response to the 2003 Quantification Settlement Agreement. This trade is based on increasing conservation of irrigation water in the Imperial Irrigation District.
Maintaining flows in rivers to support ecosystems is very important. Brian Richter has worked on this topic for decades. Originally termed minimum instream flows in the 1950s, our understanding of ecosystem requirements has improved. Environmental flows now consider variable flow requirements for ecosystems including high pulse flows (floods).
Example: Rio Grande River study evaluating water requirements for 11 selected species to develop integrated environmental flow requirements for river species and ecosystems.
Quantifying environmental flows is extremely time consuming. Richter and others, River Res. & Applic. (2012) developed presumptive flow standards as a stopgap, mostly ranging from 80 – 90% of total streamflow. This is a very conservative number and some studies indicate environmental flows can be as low as 26% in a study in China (Liu and others, Ecol. Indic., 2016).
Case example in India where deceased bodies are placed on wooden rafts in rivers and lit on fire, needed to estimate water requirements for environmental flows in rivers such as the Ganges to accommodate this practice.
Texas legislature provides funding to estimate environmental flows through Senate Bills 2 and 3 (Texas Water Development Board Environmental Flows).
Yangtze River in China: study determined that flow requirements for carp required ~10 days of abrupt rise in the Yangtze River to promote fish spawning and Three Gorges reservoir outflows are being managed to accommodate this (Ban and others, Ecol. Engin, 2018).
Great Salt Lake drying up because of overuse of water feeding the lake (Randall, Science News, 2023). Great Salt Lake is a large shallow (average 4 m deep) endorheic lake (internally draining). An estimated 71% of the water in the streams feeding the lake is used for irrigated agriculture. The lake has lost 2/3rd of volume and half of its areal extent. Exposure of dry lake bed increases air pollution (2 million people exposed along Wasatch Front including Salt Lake City).
Great Salt Lake is 3 – 5 times the salinity of seawater and supports the worlds largest brine shrimp cysts, exporting 40% of the global supply. Aquaculture is fueled by brine shrimp, producing about half of the worlds commercial seafood. The shrimp population almost collapsed in 2022 (Larsen and Bridges, Salt Lake Tribune, Jan. 2024).
In his book Chasing Water (Fig. 3) Brian Richter uses a bank balance analog to describe relationships between water supplies and demands and deficits. We have the same amount of water on the planet but locally demand often exceeds supplies. The book includes options for resolving water bankruptcy with a Water Toolbox highlighting seven principles:
- Build a shared vision for your community’s water future
- Set limits on total consumptive use of water
- Allocate specific volumes to each user, then monitor and enforce
- Invest in water conservation to its maximum potential
- Enable trading of water rights or permits
- If too much water is being consumptively used, subsidize reductions in consumption
- Learn from mistakes or better ideas, and adjust as you go
The book includes many wonderful examples from different regions globally based on Brian's work with The Nature Conservancy.
