Mark L. Johnson
Water Woes IX-Water Study Session Report Part B
Water Is The Sustenance Of Life
In Part A we reported that Marana Water has 2,804 acre-feet (AF) of water remaining in its Designated Assured Water Supply (DAWS) account. This is equivalent to 9,347 residential lots. Marana can process (platting & other approvals) about 835 lots per year. Therefore, the current DAWS account will be exhausted in the year 2032. We also learned that the Marana Planning Commission has approved a multitude of subdivisions of which there is no DAWS to serve 16,420 lots.
In Part B we will look into the current DAWS water supply sources/issues and Marana Water's future.
For reference, click on the Button below to view the Marana Water Study Session PowerPoint presentation.
Water Study Session Report-Part B
Designated Assured Water Supply (DAWS)-Water Sources
Marana Water's DAWS [7,580 acre-feet/year (AFY)] consists of; (1) Central Arizona Project (CAP) Colorado River water, (2) Recycled Wastewater (Effluent), (3) Long-term Storage Credits and (4) Groundwater as shown in the attached graphics (referenced in the PowerPoint and in Know Your H20 Part X-Marana Water & Tucson).
Let's take a closer look at these water sources and the issues associated with each:
CAP Water [2,336 AFY]-Marana's Colorado River Water allocation delivered via CAP. Long-term renewable source but subject to Colorado River shortage cuts.
Recycled Wastewater (Effluent) [1,681 AFY]-treated effluent from Marana's wastewater plant (s) that is treated and recharged into the aquifer. About 55% of residential water usage returns to the sewer as wastewater and this source will only increase if the population increases.
Long Term Storage Credits (LTSC) [169 AF])-excess groundwater replenishment water available in future years. Minor source subject to cuts and depletion.
Groundwater [3,394 AFY]-groundwater that must be replenished by the Central Arizona Groundwater Replenishment District (CAGRD). CAGRD may not have the water and much of its portfolio are short-term contracts and subject to cuts. CAGRD water is also very expensive. A portion of the aquifer underlying Marana is polluted with PFA's. Although it is treated, the concentration of these contaminants could increase with continued pumping as it did in Tucson.
Marana Water's Future
Marana Water's future is not as rosy as some in Marana government would have you believe. With good science/engineering, conservative assumptions and professional water management, we can develop a plan to ensure existing and future water customers have a long-term and bonafide water supply.
Prior to the Water Study Session TA called out some critical water management action items (see TA Alert! Water Study Session). Let's see how the Study Session information aligns with these action items.
DAWS Transparency- √ Slide 23 indicates there will be a dedicated webpage, public outreach and citizen feedback.
Groundwater Modeling- √ Slide 21 shows that updated regional groundwater modeling will be conducted.
Drawdown/Safe Yield-not mentioned but the 1,000' drawdown allowance should not be allowed to determine DAWS. Safe Yield should be defined as a groundwater surplus based on the 20-year running aquifer balance of inflows and outflows.
Reliable & Renewable Water Supply-not mentioned but all Marana Water DAWS sources must be existing (not projected) reliable and renewable with executed permanent contracts to cover the 100-year DAWS requirement. This includes CAGRD water supplies that are supposedly planned to serve Marana Water. These water supply sources would include Colorado River Water via the Central Arizona Project (CAP), recycled wastewater and other permanent, reliable and renewable water sources.
Colorado River Water Reliability Factor-not mentioned but Marana Water must utilize a 75% reliability factor for its Colorado River Water supply, i.e. only 75% of the allotment can be used in calculating DAWS due to the long-term drought & aridification, potential water cuts, groundwater pollution, etc.
Water Demand Projections-√ Slide 13 shows that water demand projections are based on 0.3 AFY/residential lot and commercial water usage is also included.
50-Year Water Management Plan-√ As shown in Slide 21, Marana will begin an Integrated Water Resource Planning effort that will include drought preparedness and water conservation programs. The proposed planning period of 15-20 years is too short. Marana Water should refrain from submitting a DAWS application until it completes a comprehensive 50-year Water Management Plan that incorporates Items 1-6.