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Targeted Brush Control in the E.V. Spence Reservoir Watershed

Final Report

Funding provided through a CWA §319(h) Nonpoint Source Grant from the

Texas State Soil and Water Conservation Board and the

U.S. Environmental Protection Agency

TSSWCB Projects 03-06 and 00-11

Executive Summary

The E.V. Spence Reservoir (Segment 1411) was placed on the State of Texas 1998 Clean Water Act

Section 303(d) List because sulfate and total dissolved solids (TDS) concentrations exceeded the water

quality standards criteria of 450 mg/L, and 1500 mg/L, respectively. These loadings are a result of both

natural and man-made, nonpoint source pollution which is prevalent in numerous locations within the

basin. Improper brine disposal, leaking oil well casings, and the over-pressurization of down-hole

formations are the prime sources of the man-made pollution. Surface water traveling across mineral beds

such as salt flats, the dissolution of natural underground mineral deposits, and the concentration effects of

certain types of plants are the primary causes of the natural pollution.

The proliferations of invasive species of brush into the western portions of Texas are a recognized

problem in water management. Three species that occur in the E.V. Spence Reservoir watershed include

juniper, saltcedar and mesquite. These plants have a high water consumption rate and easily out-compete

most native species. A single mature plant can absorb as much 200 gallons of water a day. Because salt

cedar is a deciduous plant, salt stored in the leaves is concentrated at the soil surface when leaves are

dropped in the fall. Saltcedar is especially detrimental to water quality because of its ability to transport

salts from ground water to its leaves. Saltcedar can tolerate chloride concentrations as high as 35,000

mg/L, much higher than most plant species. This makes it almost impossible for native species to take

root.

In 1999, the Texas Commission on Environmental Quality (TCEQ) and the Colorado River Municipal

Water District (CRMWD) developed two Total Maximum Daily Loads (TMDLs), one for sulfate and the

second for TDS, with the primary focus area being on segment 1412 of the Colorado River between Lake

J.B. Thomas and the E.V. Spence Reservoir. In August 2001, the TCEQ adopted the Implementation Plan

for Sulfate and Total Dissolved Solids TMDLs in the E.V. Spence Reservoir. The goal of the

implementation plan (I-Plan) is to achieve reductions in annual-average concentration and total-annual

loading of sulfate and TDS in the E.V. Spence Reservoir watershed. The Texas State Soil and Water

Conservation Board (TSSWCB) utilized Clean Water Act (CWA) Section 319(h) funds to initiate a

project entitled Targeted Brush Control in the E.V. Spence Reservoir Watershed to implement the

targeted brush control measures described in the I-Plan.

The goal of the Targeted Brush Control in the E.V. Spence Reservoir Watershed project was to

chemically treat saltcedar in riparian areas along the Colorado River and its tributaries below Lake J.B.

Thomas to the E.V. Spence Reservoir in an effort to reduce nonpoint source pollution loadings resulting

from invasive brush species on agricultural land. The TSSWCB also provided technical and financial

assistance to agricultural producers within the Champion Creek Reservoir watershed for targeted brush

control activities. It was estimated that targeted brush control would increase water yield 3,843 acre-feet

per year to the E.V. Spence Reservoir. An increase in water yield will in return reduce pollutant

concentrations. If all management practices prescribed in the I-Plan were implemented, an estimated 39%

pollutant reduction will be achieved.

The saltcedar spraying was scheduled to be carried out over a period of three years beginning in 2004.

However, in 2004 saltcedars were attacked by a scale insect which caused early senescence. Experts

recommended postponing spraying until the following year because the compromised leaves would not

provide ideal conditions for absorption and translocation of the herbicide to the roots. During the

remaining project years of 2005 through 2007, a total of 11,391 acres were treated.

Introduction

The E.V. Spence Reservoir is a 15,893-acre reservoir located in the upper Colorado River Basin, located

approximately 2 miles west of Robert Lee, Texas (Figure 1). The Reservoir was completed in 1969 and is

owned and operated by the CRMWD. E.V. Spence Reservoir is an important water supply for the

surrounding region. It provides a portion of the water for 305,000 residents of the cities of Big Spring,

Coahoma, Midland, Odessa, Robert Lee, San Angelo, and Stanton. Additionally, the reservoir serves

mining and industrial uses, and it is a popular destination for recreational fishermen.

Water quality testing found that excessive levels of sulfate and TDS were affecting the lake and its use for

drinking water. As a result, the E.V. Spence Reservoir (Segment 1411) was placed on the State of Texas

1998 CWA 303(d) List because sulfate and TDS concentrations exceeded the segment water quality

standards criteria of 450 mg/L, and 1500 mg/L, respectively. These loadings are a result of both natural

and man-made nonpoint source pollution, which is prevalent in numerous locations within the basin.

Improper brine disposal, leaking oil well casings, and the over-pressurization of down-hole formations are

the prime sources of the man-made pollution. Surface water traveling across mineral beds such as salt

flats, the dissolution of natural underground mineral deposits, and the concentration effects of certain

types of plants are the primary causes of the natural pollution.

In 1999, TCEQ and CRMWD began developing two Total Maximum Daily Loads (TMDLs), one for

sulfate and the second for TDS, for segment 1412 of the Colorado River between Lake J.B. Thomas and

the E.V. Spence Reservoir. The TCEQ approved the TMDLs on February 9, 2001 and submitted them to

the U.S. Environmental Protection Agency (EPA) for final review and approval. The TMDLs required

load reductions between 38% and 39% for chloride, sulfate, and TDS in the E.V. Spence Reservoir.

On August 10, 2001, the TCEQ adopted the Implementation Plan for Sulfate and Total Dissolved Solids

TMDLs in the E.V. Spence Reservoir to implement the two TMDLs. This implementation plan (I-Plan)

was designed to achieve the reductions in the annual-average concentration and total-annual loading of

sulfate and TDS in the E.V. Spence Reservoir watershed as defined in the approved TMDLs. Together,

the TMDL and the I-Plan serve as the mechanism to reduce the pollutant, restore the full use of the

waterbody and remove it from the 303(d) List.

Figure 1. Upper Colorado River Basin

To achieve the needed reductions, the following suite of measures were outlined in the I-Plan: 1) point

source controls, 2) modification of reservoir operations, 3) water quality diversions, 4) oil well plugging,

5) weather modification, 6) remediation of magnesium plant site, and 7) targeted brush control. If all

management practices prescribed in the I-Plan are implemented, an estimated 39% pollutant reduction

will be achieved.

The proliferations of invasive species such as juniper, saltcedar and mesquite into the E.V. Spence

Reservoir watershed are a recognized problem in water management. These plants have a high water

consumption rate and easily out-compete most native species. Saltcedar is especially detrimental to water

quality because of its ability to transport salts from groundwater to its leaves. A single mature plant can

absorb as much as 200 gallons of water a day. Because saltcedar is a deciduous plant, salt stored in the

leaves is concentrated at the soil surface when leaves are dropped in the fall. Saltcedar can tolerate

chloride concentrations as high as 35,000 mg/L, which is much higher than most plant species. This

makes it almost impossible for native species to take root.

In the I-Plan no additional mass loadings were assumed to accompany the runoff originated from brush

control. It was estimated that targeted brush control would increase water yield 3,843 acre-feet per year to

the E.V. Spence Reservoir. This increase in water yield will reduce pollutant concentrations. The

TSSWCB utilized Clean Water Act §319(h) funds to initiate a project entitled Targeted Brush Control in

the E.V. Spence Reservoir Watershed to implement the targeted brush control measures described in the I-

Plan.

Materials and Methods

The foundation of this project was the TSSWCB working cooperatively with the Upper Colorado Soil and

Water Conservation District (SWCD), Mitchell SWCD, Coke County SWCD, CRMWD, Texas

Department of Agriculture (TDA), Texas Parks and Wildlife Department (TPWD), U.S. Fish and Wildlife

Service (USFWS), Natural Resource Conservation Service (NRCS), Texas AgriLife Extension Service,

and others in an effort to reduce nonpoint source pollution loadings resulting from invasive brush species

on agricultural land. These targeted brush control activities will be conducted as prescribed in the I-Plan

for E.V. Spence Reservoir. The goal of the project was to chemically treat saltcedar in a 150 foot corridor

along the Colorado River and its tributaries below Lake J.B. Thomas to the E.V. Spence Reservoir. It has

been estimated that 95% of all saltcedar in the watershed exists within the riparian areas.

It was decided that aerial application

of Arsenal herbicide from a helicopter

was the most efficient and cost-

effective way to treat saltcedar. The

State of Texas issued an Invitation for

Bids and a qualified expert was

selected to conduct the aerial

application.

Arsenal is a product better known for

its use for brush control on utility

right-of-ways. The State of Texas had

to obtain an EPA Section 24(c)

“Special Local Needs” Label so that

Arsenal could be applied in riparian

areas adjacent to the habitat for the

Texas poppy-mallow, a federally endangered plant species. Prior to February 2003, Arsenal could not be

applied in Coke, Runnels and Mitchell Counties due to the presence of Texas poppy-mallow. Texas

Department of Agriculture, Texas AgriLife Extension Service, and the CRMWD worked with EPA and

USFWS to revise the 24(c) Label to include the counties above. Subsequent to receiving the 24(c) Label,

BASF added an aquatic label (Habitat) for the active ingredient (Imazapyr) in Arsenal. Habitat was used

in the latter stages of the project primarily in the E.V. Spence lake basin where a significant infestation of

saltcedar was present in waters of the reservoir.

To prevent impacts to the federally endangered Texas poppy-mallow, all aerial applications within ¼ mile

of Tivoli or Brownfield sands in Coke, Runnels and Mitchell counties were made by helicopter using

controlled droplet nozzles, boom configurations, and air speeds below 60 mph to achieve an average

spray droplet size of 1000 microns or greater. In addition, a 60 foot aerial spray buffer in topography or

lateral distance from the Tivoli and Brownfield sands was maintained at all times. Aerial spraying was

conducted between August 15 and October 15, the dormant season for the Texas poppy-mallow.

The estimated life of a one-time chemical treatment is approximately 15 years. To extend the life of these

chemical treatments, the USDA-Agricultural Research Service (USDA-ARS), through a Clean Water Act

§319(h) nonpoint source grant from TSSWCB (project 03-11), has been conducting studies using Chinese

leaf beetles (Diorhabda elongate) as a biological control for saltcedar. Located on Beals Creek (Figures 2

and 4), the project site is approximately 10 km and will demonstrate the effectiveness of the leaf beetle in

controlling existing stands of saltcedar, saltcedar regrowth following herbicidal treatments and the effects

of this control on recovery of native plant and animal communities and on water conservation. The

effectiveness of the beetles in controlling saltcedar will be determined by monitoring beetle populations,

dispersal and damage to saltcedar trees and any damage to non-target plants, by ground level surveys

along transects outward from the release sites at the peak of last-instar larval populations during each

generation, and by remote sensing (low-level aerial photography). The effects of biological control on

recovery of native plant and wildlife (bird) communities will be monitored annually, during mid to late

spring. Results and success of the Chinese leaf beetle demonstration will be available in summer 2008.

The TSSWCB is also responsible for managing brush in areas where brush is contributing to a substantial

water conservation problem and designates areas of critical need in the state in which to implement the

State Brush Control Program. The TSSWCB designated the Champion Creek Reservoir watershed as an

area of critical need and provided $716,354 of State Brush Control Program funding to manage brush on

15,000 acres. This should not only improve conditions in Champion Creek Reservoir, but should also

contribute to improvements to E.V. Spence Reservoir and help in the implementation of measures

outlined in the TMDL.

In order to measure the success of the implementation efforts, the CRMWD has been conducting water

quality monitoring, enhancement and water diversion on the Colorado River for a number of years. It has

collected a great deal of data for the Clean Rivers Program (CRP) and is using this dataset to evaluate and

monitor water quality of the Colorado River. CRMWD continues to monitor the water quality of Lake

Spence to further determine the success of implementation efforts.

Results and Discussion

The aerial application of Arsenal to treat saltcedar in a 150 foot corridor along the Colorado River and its

tributaries below Lake J.B. Thomas to the E.V. Spence Reservoir (Figure 2.) was scheduled to be carried

out over a period of three years beginning in 2004. However, in 2004 saltcedars were attacked by a scale

insect which caused early senescence. Although it did not damage the plants significantly, experts

recommended postponing spraying until the following year because the compromised leaves would not

provide ideal conditions for absorption and translocation of the herbicide to the roots.

Figure 2. Overview Map of Saltcedar Treatment Area

In August 2005, aerial application of Arsenal began along the Colorado River below Lake J.B. Thomas

down to Colorado City (Figure 3). A total of 2,416 acres were treated from August 18, 2005 through

September 4, 2005.

Figure 3. Year 1 (2005) Saltcedar Treatment Area

During the second year of spraying, approximately 1500 acres were treated starting just south of Colorado

City along the Colorado River, Beals Creek, and the Champion Creek Reservoir basin (Figure 4).

Spraying began on August 28, 2006 and ended on October 7, 2008.

Figure 4. Year 2 (2006) Saltcedar Treatment Area

During the final year of the project, 7,475 acres of saltcedar were treated between August 16, 2007 and

September 22, 2007. Treatment included spraying areas along the Colorado River beginning where the

2006 treatment ended down to the dam and included the E.V. Spence lake basin (Figure 5).

Figure 5. Year 3 (2007) Saltcedar Treatment Area

Conclusion

The primary objective of this effort was to aid in implementing the I-Plan for Sulfate and TDS TMDLs in

the E.V. Spence Reservoir by chemically treating saltcedar in riparian areas along the Colorado River and

its tributaries in an effort to reduce nonpoint source (NPS) pollution loadings resulting from invasive

brush species on agricultural lands. During all three years of spraying, 11,391 acres of saltcedar were

treated from below Lake J.B. Thomas to the E.V. Spence Reservoir lake basin (Figure 7.).

At this time it is too early to distinguish the extent of the water quality improvement from this project,

however there has been significant progress toward reaching the measures of success in the TMDL. Local

efforts to manage nonpoint and point source pollution have led to the gradual reduction and compliance of

chloride and sulfate levels. To date, TDS levels have improved, and are approaching water quality

standards. The annual mean concentrations for chlorides and sulfate in 2005-6 were in compliance at all

times, an enormous improvement from previous years. This is attributed to several factors including good

rainfalls and exceptional work by the CRMWD to accurately manage their diversions using real-time

water quality monitors. The mean concentration for TDS was in compliance 33% and 75% of the time

during 2005 and 2006, respectively. The annual mean concentrations of all constituents in 2007 were very

similar to levels in 2005. See Figure 6 for a record of the annual mean concentrations of these constituents

since 1968. CRMWD will continue to monitor the water quality of Lake Spence to further determine the

success of implementation efforts.

Figure 6. Annual Mean Salt Concentrations in the E.V. Spence Reservoir

Figure 7. Years 1-3 (2005-2007) Saltcedar Treatment Area