• Mark L. Johnson

Water Woes IV-Plan For Worst Case

Updated: Jul 11


Salton Sea-Imperial County, California-2018


Over the last four months there have been at least three studies released regarding the current drought and its impact on water supplies in Arizona. The following presents a summary review of these three studies which all point to a water supply disaster. Action needs to happen now to prevent the worst case scenario like the one that is happening at Salton Sea (intrinsically linked to the Colorado River) in Imperial County, CA only 350 miles from Marana. See photo above.


To help better understand water supply in Arizona, suggest first reading the Know Your H2O Series Parts I-XI.

White Paper 6-Alternative Management Paradigms for the Future of the Colorado and Green Rivers


White Paper 6-Alternative Management Paradigms for the Future of the Colorado and Green Rivers casts doubt on the ability of the current western water bureaucracy to sustainably manage the Colorado River. This white paper was published by 12 scientists at the Center For Colorado River Studies-Utah State University.


The major conclusions gleaned from White Paper 6 are:



  • Millennium Drought (2000-2018) is probably the new normal with average annual Colorado River flow at 12.4 million acre-feet per year (maf/year) (1).

  • Projected Upper Basin consumptive use is too high and current Lower Basin shortage reductions are too low.

  • Climate change (study used 6.5% decrease in flow with each degree of Celsius rise in temperature) exacerbates the supply/demand imbalance.

  • Law of the River does not provide the flexibility required to sustainably manage the Colorado River system (1).

  • Twenty-four alternative management strategies are presented including the scenario whereby Lake Powell and Lake Mead are consider as a single reservoir (2).


Hydroclimate Analysis Lower Santa Cruz River Basin Study



Hydroclimate Analysis Lower Santa Cruz River Basin Study was prepared by the US Bureau of Reclamation and published in May 2021. This study utilizes climate change and hydrology models to forecast "worst case" and "best case scenarios" for two periods: 2030's (2020-2049) and 2060's (2050-279).


Table ES-1 (below) shows changes in temperature and precipitation for the worst and best cases for each period. For all cases and periods it is predicted that temperature will rise in the Lower Santa Cruz River Basin. Precipitation will decrease in all cases and periods except the best case scenario in the 2030's.


Streamflow follows the same pattern with increases in monsoon and winter seasons in both periods for the best case scenario but large streamflow decreases for the worst case scenario in the 2030's which moderate in the 2060's. However, under both scenarios and both periods the number of dry stream days increases. See Figure ES-3 below for the worst case scenario.




The Myth of Safe Yield: Pursuing the Goal of Safe Yield Isn't Saving Our Groundwater






The Myth of Safe Yield: Pursuing the Goal of Safe Yield Isn't Saving Our Groundwater was published by the Arizona State University (ASU) Kyl Center for Water Policy in May 2021. This is the best recent water publication as it gets to core problems and provides great recommendations that actually support those presented in Know Your H2O-Part XI Conclusions.


Here is a summary of the report:




  • Arizona is not on track to achieve sustainable safe yield (water out equals water in) 41 years after establishing the Groundwater Management Act.

  • Water conservation is a good thing but will not help achieve safe yield as water demands related to growth are outpacing conservation savings.

  • Perpetual grandfathered groundwater rights exceed the amount available for achieving safe yield conditions.

  • The term safe yield has different definitions and needs to be consistent. See Know Your H2O-Part XI-Conclusion for our suggested definition.

  • Achieving safe yield on an Active Management Area basis does not consider subbasins where groundwater withdrawals could exceed safe yield on a localized basis.

  • Central Arizona Groundwater Replenishment District (CAGRD) has promised to replenish areas served by water purveyors with Assured Water Supplies (100 years) but it is doubtful that CAGRD has the long-term supplies to back it up.

  • Reduce the maximum 1,000' groundwater withdrawal depth to ensure a sustainable amount of groundwater indefinitely.

  • Deny Certificates of Assured Water Supply if sufficient renewable water supplies do not exist.


Conclusions


All three recent studies/reports conducted by reputable universities and public agencies have similar conclusions and recommendations:


  • Climate change will cause temperatures to rise and overall precipitation to lessen resulting in lower amounts of water available for public water supply.

  • Water bureaucrats have planned for the Best Case scenarios but should be planning for the Worst Case scenario.

  • Arizona's Groundwater Management system will not achieve sustainable safe yield and needs to be re-engineered.

The authors (Ferris & Porter) of the Kyle Center report said it best:


"Our analysis shows that Arizona continues on a path of unsustainable groundwater use that threatens the health and welfare of our state. It is not too late for a course correction, but that will require that Arizonans face the truth and make bold choices. It will also demand courageous leadership."


Marana Water Challenge


This is the big challenge for Marana. The Marana Water service area has 33,631 approved lots which are not currently built. That equates to 10,089 acre-feet/year (33,631 x 0.3 acre-feet/year/lot). Marana's current water usage is 2,366 acre-feet/year. This results in a total existing and approved water demand of 12,455 acre-feet/year. Yet Marana's current Designated Assured Water Supply (DAWS) is only 7,580 acre-feet/year. Marana has obligated 4,875 acre-feet/year of water more than the approved DAWS! This is a situation that will require bold choices and courageous leadership!