COLORADO RIVER Risk Study Update

Transcription

1 COLORADO RIVER Risk Study Update September 14, 2018 Eric Kuhn

2 OVERVIEW HOW IS THE RIVER OPERATED AND MANAGED? WHY DID WE CONDUCT THE RISK STUDY? RESULTS AND IMPLICATIONS FOR THE FUTURE

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4 1922 Colorado River Compact Divides the Colorado orado River (incl tributaries), into an Upper and Lower Basin Boundary between the two basins is Lee Ferry, Arizona Lower Division: Nevada, California & Arizona Upper Division: Wyoming, Colorado, New Mexico & Utah Arizona, Utah and New Mexico have lands within both Arizona, basins

5 Colorado River Compact of 1922 Colorado, like all Upper Division states, shares obligations to the Lower Division III (d) the Upper Division shall not cause the flow of the river at Lee Ferry to be depleted below an aggregate of 75,000,000 acre acreacre-feet for any ten consecutive years. III (c) regarding Mexico the Upper Division must deliver at Lee Ferry water to supply one-half one-half of the one deficiency so recognized in addition to that provided in paragraph (d).

6 Upper Colorado River Basin Compact of 1948 Purposes of the 1948 Compact include: equitable division and apportionment of the use of the waters apportioned in perpetuity to the Upper Basin establish the obligations of each State of the Upper Division with respect to deliveries of water required to be made at Lee Ferry procedures and methodology for determining how much water Colorado would have to provide in the event the curtailment of the use of water becomes necessary in order that the flow at Lee Ferry shall not be depleted below that required by Article III (of the 1922 Compact) ct).

7 Upper Colorado River Basin Compact of 1948 Provides Arizona with 50,000 AF per year, the remainder as follows: 51.75% to Colorado 23.00% to Utah 14.00% to Wyoming 11.25% to New Mexico Consumptive use is defined as man-made depletions to the natural (undepleted) flow at Lee Ferry. (NOTE: This definition includes CRSP reservoir evaporation.)

8 RIVER OPERATIONS LAW-OF-THE-RIVER IS THE GUIDE BUT DETAILS, DETAILS..DETAILS 1968 ACT REQUIRES THE SOI TO PREPARE LONG RANGE OPERATING CRITERIA AND ANNUAL PLANS SOI MUST CONSULT WITH THE STATES BUT HAS FINAL SAY 2007 IGS CONTROL MEAD & POWELL

9 Lake Powell Releases Controlled by the 2007 Interim Guidelines Based on storage levels in both Powell & Mead What happens in the LB impacts Powell and what happens in the UB impacts Mead As long as Powell has storage - NO compact problems for UB

10 WHY DO A RISK STUDY? FULL(OVER) DEVELOPMENT AND LOW HYDROLOGY (SINCE 2000) UPPER DIVISION STATES PLANNING INCLUDES DEMAND MANAGEMENT COLORADO S WATER PLAN #4 OF THE FRAMEWORK ALSO INCLUDES DEMAND MANAGEMENT

11 What if drought periods of past 25 years repeated? - Current conditions at Powell: about half full summer Three recent droughts superimposed on current conditions (drawdowns based on historical record) - No contingency planning actions in place; no water banking in place Elevation 3525: Threshold for Lower Operating Tier; Reclamation is concerned about Hydropower efficiency and hydraulics/cavitation below this level Elevation 3490: Ability to make releases per 2007 Interim Guidelines (and hence Compact Compliance) is jeopardized

12 Contingency Planning Challenge from US Dept of Interior: What if the current drought were to continue into the future? Have a plan in place by 2018 (MOA or similar) The Goal: Identify actions that can reduce the risk of losing power production or being unable to deliver water Components of the solution: Drought Response Operations of CRSP reservoirs Demand Management Cloud seeding / other augmentation

13 West Slope BRT Study Questions Addressed in Phases I&II: 1. What are magnitude and duration of Powell shortages below elevation 3525? 2. How much of the above shortages can be met by contributions from Drought Operations of CRSP reservoirs? (A: up to about 2 MAF) 3. How much consumptive use reduction ( demand management ) would be needed by Upper Basin states - AFTER use of stored CRSP water - in order to maintain Powell pool elevations? (A: in extended droughts well over a million acre-feet) 4. What are possible implications to Compact deliveries? (A: storage in Powell is key-if storage available no Compact problems) What is range of volumes that Colorado might need to conserve? (A: up to a million af too much for one year must use a water bank to build up a reserve) 5. Can we use CRSS & StateMod together to answer detailed questions? (A:yes) We must understand the Big River issues in order to address issues within Colorado. CRSS handles the Big River, StateMod is used to look at detailed management and impacts within Colorado

14 CRITICAL ASSUMPTIONS We ll take action at 3525 to protect min power (3490 ) 3525 = 2 MAF above MP Lower Basin will successfully implement its DCP! Future hydrology will be similar to (nat Lee Ferry of about 13.2 MAF since 2000 it s 12.4)

15 Conclusions Hydrology, Demands and Future Development levels matter, the higher the consumptive use in the UB the higher the risk to all users. Contingency Planning is Essential, CRSP reservoir drought operations reduces the risk, but in more severe droughts (e.g., & ), demand management is also required. Some of the demand management volumes are very large, so we need to consider the trade-offs and alternative strategies we need management storage in Powell and other places. Demand Management Combined with a Water Bank: Could limit the Annual impact to CU by spreading Conservation over many years- 50K over ten years = 500K Would provide greater control over conserved water

16 POINTS TO CONSIDER Phase III (more details on DM alternatives and impacts) now in progress. DCPs have not yet been approved within individual states FE Arizona IGs expire in 2026 New OC/IGs must be negotiated (will impact DCPs) Federal legislation will be required.

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19 1,225 1,200 1,175 January % Active Storage Lake Mead Elevation Since 2000 Structural Deficit 1,150 1, MAF Release WY ,100 1,075 1,050 1,025 Hydrology 1, Projected Month Lake Mead Elevation (EOM) Projected 24 Month 8.23 MAF Releases First Shortage Tier