Interim Water Committee

October 30, 2013

40% of Colorado’s Ag Receipts are Generated in the South Platte Basin 830,000 Irrigated Acres

• Predevelopment Groundwater flow

• Initial Pumping Impact

• Expanding cone of depression

• Changed gradient to stream. Impact can last years.

Sterling, CO

HB1278: What’s Happening to Groundwater Levels in the Basin?

High-water conditions have occurred throughout the basin between 1953-2013

Groundwater is rising in many locations over last decade, 2003-2012

HB1278: What is the status of groundwater use in the Basin?

Location of High Capacity Wells in the S. Platte Alluvial Aquifer.

High Capacity Irrigation Well Count By Water District.

Annual Groundwater Pumping in Water Districts 2, 1 and 64 (AF/yr)

Groundwater Pumping

• Prior to early 2000s, annual variability of pumping can be attributed to varying climate conditions, and changes in irrigated acreage to a lesser degree

• Reduced pumping after 2003 reflects administrative changes and abandonment of wells

• Pumping increased in late 2000s as augmentation sources were secured

HB1278: Is Augmentation Protecting Senior Water Rights?

Augmentation Plan Requirements – 2, 1 and 64

Augmentation Requirements

• Not all ground water pumping causes depletions to the river; and depletions do not require augmentation if there is not a senior call on the river

Location of Existing Recharge Structures in the S. Platte Basin.

Artificial Groundwater Recharge in Water Districts 2, 1 and 64.

Augmentation Plan Supply vs. Augmentation Plan Requirement Water Districts 2, 1 and 64

Augmentation Plan Supply vs. Augmentation Plan Requirement

Augmentation Plan Supply vs. Augmentation Plan Requirement

Augmentation Plan Supply vs. Augmentation Plan Requirement

Augmentation Plan Supply vs. Augmentation Plan Requirement

WD 2 WD 1 WD 64 Total

Total Surface Diversion 292,604 673,869 247,444 1,213,916

Total Pumping 31,195 177,490 110,612 319,298

Groundwater Consumptive Use

23,138 134,872 80,781 238,791

Total Augmentation 29,652 137,354 97,312 264,318

5 year Average (2008-2012) in AF/Year

Observation

• Due to the requirements of augmentation plan decrees and the timing of recharge pond accretions, recharge augmentation supplies must be taken in advance of requirements (i.e. users must “hedge” their bets).

HB1278: What’s Happening to Surface Flows in the Basin?

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ANNUAL SOUTH PLATTE RIVER FLOWS AT JULESBURG, CO

5 Year Moving AverageDWR PLAJUCCO.06764000.SOUTH PLATTE RIVER AT JULESBURG

Min: 30,355 AF Max: 2,130,245 AF Mean: 380,070 AF Median: 266,538 AF

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ANNUAL SOUTH PLATTE RIVER FLOWS AT JULESBURG, CO

5 Year Moving AverageDWR PLAJUCCO.06764000.SOUTH PLATTE RIVER AT JULESBURG

Min: 30,355 AF Max: 2,130,245 AF Mean: 380,070 AF Median: 266,538 AF

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ANNUAL SOUTH PLATTE RIVER FLOWS AT JULESBURG, CO

5 Year Moving Average Cummulative AverageDWR PLAJUCCO.06764000.SOUTH PLATTE RIVER AT JULESBURG

Min: 30,355 AF Max: 2,130,245 AF Mean: 380,070 AF Median: 266,538 AF

HB1278: What’s Happening to Water Use by Phreatophytes?

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Seasonal Phreatophyte ET (1990, 2001, and 2010)

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Phreatophytes Consume 250,000 – 300,000 AF/yr Non-Beneficial ET has increased by Over 30% Since 1990.

Summary, part 1 • Groundwater levels are rising in some areas in the S. Platte

• On a basin scale, augmentation supply has caught up with augmentation requirements in recent years, but many localized issues remain.

• Senior surface water rights are being protected under current administration of the system.

• The long-term average annual flow at the Julesburg gage near the state line averages 380,070 AF. The average annual flow for the period of 2000-2012 was 213,446 AF.

Summary, part 2

• Many of the groundwater problems observed are localized, and care must be exercised not to over-reach when applying solutions.

• The current system is accepted and working well for many water users (but not all); the question remains as to whether we can improve the system for the good of the whole while addressing local problems.

• There is insufficient water to meet all of the needs and this will only get worse in the future - More water storage will help both surface and groundwater users in the S. Platte.

http://www.cwi.colostate.edu/southplatte/index.html