By Jared Hodes
Los Angeles water use and conservation are pressing issues today and will only become more pertinent as we move forward into the future. The population will continue to increase which means that total water demand will increase unless there are significant increases in conservation efforts to reduce the per capita water demand. Los Angeles has actually done a relatively good job of keeping its overall water demand somewhat constant (as evident in the graph below), despite the continued increase in population.
Climate change will have significant impacts on residents’ ability to have the same level of access to water resources as they do at the present day. Since Los Angeles imports most of its water (as seen on home page), it is important to look at how the source areas will be impacted by climate change. The Sierra Nevada mountain range provides a great deal of the water that is used in Los Angeles because the Los Angeles Aqueduct originates not far from the mountain range and relies on snowmelt from the Sierras for water supply. Currently, water is stored as snowpack and is gradually released into the watershed that supplies the Los Angeles Aqueduct, giving the aqueduct more of a steady supply of water. As the anthropogenic effects of climate change start to affect the region due to higher concentrations of Greenhouse Gases such as carbon dioxide, these snowpacks will not melt so gradually throughout the spring/summer, but rather melt faster and earlier in the season. Much more of the snowmelt will be lost in the watershed as runoff if the snow melts faster and earlier in the season, which means that there will be less of a supply of water for the aqueduct as the spring progresses into summer since there is no way to capture the excessive snowpack melt and store it for later use.
Another problem generated by climate change and future temperature increases is that there will be less snow and more rain as a percentage of total precipitation. Snow in the Sierras is excellent for Los Angeles because the snow is a natural reservoir for future water, but if more of that snow becomes rain due to temperature increases, the snowpack will not grow to be as large as normal and more water will be lost as runoff and will be unusable to the Los Angeles Aqueduct.
Another large source of Los Angeles’s water is from the Metropolitan Water District, which buys a great deal of its water from the Colorado River. The Colorado River is already at historically low levels but if the climate continues to warm and the warming accelerates, the Colorado River water supply will diminish as more of it will be used upstream from where MWD gets its water, potentially leaving them with little to no supply of water from the Colorado River. Greater rates of evaporation due to higher air temperatures will not only affect the level of the Colorado River, but the rate of evaporation on the Los Angeles Aqueduct as that water is transported hundreds of miles to its destination.
On a more local scale, the future increase in temperature will lead to greater evaporation rates in pools and a higher water demand for people’s lawns (which are already a huge user of water). If people want to keep their lawns as time goes on and the water supply becomes more variable, it would behoove homeowners to find more water efficient and indigenous plants, or find an alternative mode of supplying water to be used outside on their lawn.
Graywater is a water source that has remained relatively untapped, but has the potential to reduce the amount of drinkable water that is wasted on watering lawns and other outdoor water uses. Graywater is household wastewater that has not been in contact with toilet waste. Graywater sources include bathtubs, showers, bathroom sinks, as well as water from dishwashers and laundry machines. These graywater sources constitute about 60% of indoor water use for single family residences. Graywater reuse techniques, if widely implemented, could save 8%-27% of all water supplied to the urban sector by LADWP (18.2 billion-60.2 billion gallons saved per year).
Los Angeles is one of the more forward thinking cities when it comes to water conservation, but will have to remain ahead of the curve in the future in order to offset the increasing population, as well as the decreased supply of water anticipated in the future.
As seen above, a much larger portion of water will come from recycling water as well as various conservation efforts including stormwater capture. As time goes on, and the effects of climate change are better quantified, conservation efforts may have to be amplified beyond what was anticipated in order to have a sustainable water supply.