Commentary and Analysis Regarding Colorado Law

As I was preparing recently to write this blog post a few weeks ago, several friends had just lost homes in the Marshall Fire that occurred in Boulder County on December 30^th, and I was reminded that my LAST blog post, dated October 22, 2020, “Climate Change Impacts on Colorado Water Users,” specifically touched on increased wildfires as a potential consequence of climate change. In October of 2020, Colorado was just coming out of one of the hottest and driest summers in recorded history.  Unfortunately, the beginning of 2022 isn’t shaping up to look much better.  As of the date of the Marshall fire, Colorado, and the country as a whole, had just experienced the hottest six months in recorded history.  The next highest six-month average temperature occurred during the 1930s, during the Dust Bowl.

The data, sourced from the National Oceanic and Atmospheric Administration, illustrated that the average Colorado temperature between July and December reached 53.4 degrees, which is over a degree and a half warmer than the same six-month span in 2020.  The next highest six-month state average was 52.1 degrees in 1933.

Recent fires and high temperatures across the West may have water users wondering what rising temperatures and sustained drought conditions might mean for Colorado water users.  While only time will tell, it’s relevant to note that the summer of 2020 was one of the hottest and driest on record.  The month of August was one of the top ten warmest Augusts on record according to the National Oceanic and Atmospheric Administration’s “August Climate Summary,” with 26 days above 90 degrees Fahrenheit and 17 days above 95 degrees!  Denver received only 0.35 inches of precipitation in August, which is 1.34 inches below normal, and there were only 5 days total during the month with measurable rainfall at all.

What does this mean for Colorado water users?  Changes in temperature and precipitation can impact snowpack, length of crop seasons and quantities produced, wildfires, and pests, just for starters.  According to the US EPA, snowpack in the western United States has been decreasing since the 50’s, and the amount of snowpack measured in April at Colorado sites specifically has declined by 20-60%, on average.  Diminishing snowpack can mean less spring/summer runoff, which typically provides much of the water needed by agricultural and municipal water users.  Earlier runoff can mean changes in the priority system relied upon by Colorado water users, as many decrees for reservoirs (typically relied on to capture spring runoff for later summer use) have limitations on when such storage can start and when it must stop.  Rising temperatures can also increase evaporation from soil, crops, and storage reservoirs, meaning more water is lost to the air than usual.  Soils may become drier as evaporation rates increase, which can mean they retain more water when there IS precipitation so that less water is ultimately flowing into the state’s stream systems.  Changes to Colorado snowmelt, rainfall, and temperature patterns may also impact Colorado’s farms and ranches.  Increased evaporation can increase irrigation demands and mean that some farms change to dry land farming, which typically decreases crop yields.