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Texas Water Tour: Surface Water

Surface Water Snapshot | Print Snapshot (PDF)

Introduction

Surface water (water that is located above ground) in Texas is composed of 196 major reservoirs, 191,000 miles of streams, 15 major river basins and eight coastal basins. ^[1] Basins are areas drained by a river and its tributaries; reservoirs are large artificial lakes. (Texas has only one natural lake: Caddo Lake, located near the Louisiana border.)

There are two types of reservoirs: on-channel, created by damming rivers and restricting the downstream flow of water, as with the Highland Lakes chain in Central Texas, and off-channel, created by piping water from a river to an artificially constructed lake separate from the river itself, such as Wharton County’s new Arbuckle Reservoir (estimated to be operational in 2023).^[2]

As of 2020, surface water supplied the state with 7.2 million acre-feet of water annually. The 2022 State Water Plan (SWP) projects that by 2070 the existing supply of surface water will remain mostly stable at 7.1 million acre-feet, a decline of three percent.^[3] The total existing water supply, meanwhile, is projected to decrease by 18 percent by 2070, and groundwater supply will decrease by a whopping 32 percent (Exhibit 1). This will exacerbate the existing water shortfall of 3.1 million acre-feet to 6.9 million acre-feet by the year 2070 if nothing is done to address the state’s growing water needs.

Existing Water Supply by Source, Texas, 2020-2070 (million acre-feet)

Source	2020	2030	2040	2050	2060	2070
Surface water	7.2	7.2	7.2	7.1	7.1	7.1
Groundwater	8.9	7.6	6.9	6.4	6.1	6.0
Reuse	0.6	0.6	0.7	0.7	0.7	0.7
Water Demand	17.7	18.4	18.3	18.4	18.6	19.2

Source: Texas Water Development Board

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Surface Water Uses

Surface water accounted for 42 percent of the state’s total water use in 2019, while groundwater provided 55 percent and water reuse the remaining three percent.^[4]

Surface water availability is a critical resource for the state’s municipalities. In 2019, about half of surface water used in Texas was for municipal purposes (ranging from single-family residences to nonresidential commercial and industrial establishments), followed by nearly 30 percent for irrigation (field crops, vineyards, orchards) and 15 percent for manufacturing needs (Exhibit 2). This differs from groundwater use, in which about 75 percent was used was for irrigation and just 19 percent for municipal purposes.

Uses of Surface Water by Use Category, Texas, 2019

Indicator	Municipal	Manufacturing	Mining	Power	Irrigation	Livestock
Total Surface Water Use	2,802,549	881,233	31,652	357,459	1,745,163	133,335
Share of Total Surface Water Use	47.1%	14.8%	0.5%	6.0%	29.3%	2.2%

Source: Texas Water Development Board

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Municipal water needs (or potential shortages) are projected to rise dramatically in the coming decades, from about 215,000 acre-feet in 2020 to 3.1 million acre-feet in 2070. Municipal water needs as a share of total water needs are projected to increase from seven percent in 2020 to 46 percent in 2070. Water needs for agricultural irrigation purposes will fall from 77 percent of total water needs in 2020 to 44 percent in 2070. Total water needs are expected to rise from 3.1 million acre-feet to nearly 6.9 million acre-feet during this period, a 120 percent increase (Exhibit 3).

Water Needs by Water Use Category, Texas (acre-feet)

Year	Irrigation	Municipal	Manufacturing	Power	Livestock	Mining	Total
2020	2,395,767	214,623	159,493	187,298	40,465	118,615	3,116,261
2030	3,318,834	802,045	264,405	192,235	43,781	123,125	4,744,425
2040	3,279,822	1,371,211	275,172	196,121	48,270	110,864	5,281,460
2050	3,187,547	1,911,573	286,064	199,016	53,649	102,283	5,740,132
2060	3,093,710	2,502,456	294,768	201,048	60,432	96,486	6,248,900
2070	3,045,991	3,144,304	301,260	202,961	63,400	101,384	6,859,300
Total Change	650,224	2,929,681	141,767	15,663	22,935	-17,231	3,743,039

Source: Texas Water Development Board

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Water Management Strategies

Given increasing municipal water demands, surface water projects are a major priority of the 2022 SWP’s water management strategies for new supplies. In 2020, surface water made up about 24 percent of new water supplies in Texas^[5]. By 2070, the SWP estimates that surface water will increase to 37 percent of new water supplies, a result of water management strategies focused on surface water, including the 23 new major reservoirs recommended by regional planning groups (Exhibit 4).

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Surface Water Planning

The TWDB recommends 1,829 new surface water projects, including 23 new major reservoirs.^[6] These projects will provide the state with an additional 2.8 million acre-feet of water per year by 2070.^[7] 

Because some parts of Texas typically are much drier than others, a common strategy to meet water needs is to move water via canals or pipes between river basins in a practice called interbasin transfer. Some areas in Texas receive most of their water from interbasin transfers.

Bois D’Arc Lake, northeast of the city of Bonham in Fannin County, will be the newest reservoir in Texas and has received nearly $1.5 billion in funding commitments from the State Water Implementation Fund for Texas (SWIFT), the second largest commitment total of any project under the program.

Notable Projects

Most surface water projects are concentrated in the metropolitan areas of Dallas-Fort Worth and Houston. These areas are at the forefront of the water crisis, as both are experiencing strong population growth while lacking nearby water sources. The success of these projects is a result of careful coordination, planning and compromise between different entities and interests. Some are discussed below.

Bois D’Arc Lake

Starting construction in 2018 and set to deliver water by late 2022, Bois D’Arc Lake is the first major Texas reservoir to be built in 30 years,^[8]created to meet the expected near doubling population in the North Texas Municipal Water District (NTMWD) service area by 2050.^[9] Once completed, it will provide up to 82 million gallons per day (MGD) of water, highlighting the efficient coordination between state, local and city governments.^[10] The project is funded with a nearly $1.5 billion investment from the SWIFT program, which will save the district and its ratepayers more than $240 million in financing costs.^[11]

Arbuckle Reservoir

As the Lower Colorado River Authority’s (LCRA) latest water supply project and the first new reservoir on the lower Colorado River basin in decades, the reservoir will provide Austin with 90,000 acre-feet of water per year by allowing for the capture and storage of a significant amount of water downstream from the Highland Lakes.^[12] The lake will contain more water than Lake Austin, Lady Bird Lake and Lake Marble Falls combined.^[13] Beyond providing water to Austin, it will also provide water to downstream rice farmers.^[14] The original lifetime budget for the reservoir was $250 million, funded by a TWDB bond sale and a $2.4 million grant.^[15]

The construction of the dam, however, is not without its challenges. Due to the nature of Wharton County’s soil, the lake experienced more groundwater seepage than expected, prompting the construction of an additional subsurface seepage cutoff wall. This has delayed the completion of the dam to 2023 and required a $65 million increase to the project’s lifetime budget, approved by the LCRA Board of Directors in December 2019.^[16]

Allens Creek Reservoir Project

Just north of Houston, the Allens Creek Reservoir is a proposed water storage project by the Brazos River Authority designed to meet the surface water needs of a rapidly growing population. The reservoir is projected to provide enough water to meet the needs of 260,000 families, producing around 32.6 billion gallons of water annually. Permitting and design processes begin in 2022, and construction will begin in as early as 2030.^[17]

Harris County Surface Water Projects

Harris County set the goal of getting 80 percent of its water supply from surface water by 2035^[18] in an effort to meet the water demands of a rapidly growing population, and to address subsidence, a phenomenon where the ground sinks in elevation due to water no longer being there to “hold it up,” resulting in flooding and the formation of sinkholes.

To meet this goal, the city of Houston and several regional water authorities have partnered to share the costs of the Surface Water Supply Project (SWSP). The collaboration will produce cost savings, ease subsidence and create more efficient delivery for the region’s water needs.^[19] The SWSP consists of two key projects:

Northeast Water Purification Plant (NEWPP) Expansion Project

This multi-billion-dollar project, to be completed in phases over the next 10 years, is the largest progressive design build project of its kind in the United States. The plant will purify water purchased by the city of Houston from Lake Houston and increase the capacity of the water purification plant from 80 MGD to 400 MGD.^[20]

Luce Bayou Interbasin Transfer Project

Since Lake Houston does not hold enough water to provide the 400 MGD of water needed for the expanded NEWPP, a 26-mile system series of canals and pipes will be built from the Trinity River through the Luce Bayou to maintain the water level of Lake Houston. It will provide an additional 240 MGD of water per day to the NEWPP and Lake Houston, with a potential supply of up to 500 MGD. The project is a collaboration between the city of Houston, the West Harris County Regional Water Authority, the North Fort Bend Water Authority, the Central Harris County Regional Water Authority, the North Harris County Regional Water Authority and the Coastal Water Authority.^[21]

These projects are funded through bonds issued by water authorities, SWIFT investments and by the city of Houston.^[22]

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For additional insights, see The 2022 State Water Plan and Innovations in Texas Water Systems, Fiscal Notes, June-July 2022.