Best Bets for Texas Water

Dams & reservoirs

In Texas, reservoirs are large man-made lakes used as a source of water supply. There is only one natural lake in the state, though even that lake has been modified with a dam; the rest are artificially constructed. There are 200 manmade major reservoirs in Texas, as well as various smaller ones.

The types of reservoirs: On-channel and off-channel
On-channel reservoirs are built by damming rivers, flooding riverside habitat and cutting off much of the flow of water downstream to create a large and controlled lake.
Off-channel reservoirs are built away from the main channel of a river; instead, water is piped away from the river to fill an artificially-constructed lake.
Some “off-channel” reservoirs are hybrids that are built on the channel of a small stream but also hold water pumped from a nearby river.

There are hundreds of reservoirs in Texas, many of which were constructed during a reservoir-building frenzy in the 60s and 70s. Construction rates have since slowed down, partially because there aren’t many locations left that could be viable sites for new large reservoirs. Even so, the most recent (2017) state water plan for Texas recommends building 26 new major reservoirs.

In many cases, greater water conservation and drought response measures, along with other more environmentally-friendly supply options, could avoid these multi-billion dollar projects.

Reservoirs report card
Environment
When compared to other strategies, it’s hard to see the benefit of this one.

Reservoirs cannot be created without destroying large amounts of wildlife habitat. After they are created, reservoirs capture flows needed to support downstream fish and wildlife.

True costs
When compared to other strategies, it’s hard to see the benefit of this one.

Reservoirs are one of the most expensive water supply strategies available, and residents shoulder these costs through higher water rates. Reservoir construction also involves societal costs implicit in taking economically-valuable and/or family-owned land out of production, often through means of eminent domain.

Long-term viability
When compared to other strategies, it’s hard to see the benefit of this one.

Reservoirs become less effective over time as sediment builds up and as evaporation rates increase, which is already happening as a result of climate change.

Dams and reservoirs grade breakdown
Environmental impacts
Positive
  • None.
Negative
  • Reservoirs are created by permanently flooding land, which irreversibly destroys wildlife habitat. On-channel reservoirs flood economically- and environmentally-valuable riverside woodlands, and, like off-channel reservoirs, can destroy valuable land like prairies, farmland and wetlands.
  • Dams used for on-channel reservoirs block fish and wildlife from moving freely upstream and downstream, which can interfere with their natural feeding and spawning lifecycles, as well as destroy species diversity, which is important for healthy wildlife populations.
  • Dams used for on-channel reservoirs trap sand and silt above the dam, rather than allowing it to move naturally downstream through a river. Without these sediments, the river channel downstream often gets deeper and the banks cave in, leading to tree loss. Without trees, habitat is lost, and without the shade they provide, water temperatures may rise and create an inhospitable home for fish and wildlife. In addition, coastal bays and beaches may be deprived of sediment and sand needed to keep them healthy.
  • Reservoirs divert water away from rivers downstream; without enough flowing water from natural river flows, many plants, fish, birds and other wildlife struggle to survive. Water quality can also become a bigger issue: without healthy river flows, rivers cannot dilute pollution as well.
I feel it very emotionally, I feel it very deeply, I feel it viscerally, that with the pending threat of building a reservoir on this ranch, we're going to lose all of our dreams.
True costs

1 The lifetime costs of a reservoir and its water delivery system include construction and ongoing operation and management (such as intensive energy needs) for the reservoir itself, as well as for water treatment facilities and delivery pipelines and pumps. Eventually, reservoir infrastructure will wear out and will need to be replaced or repaired.

2 Revenue-generating farm, ranch and forest lands are often flooded and destroyed in the reservoir-creation process. When this land is privately owned and the family is uninterested in selling, the city or river authority may use eminent domain to take the land, regardless of whether the land is their source of livelihood or it has been in their family for generations.

3 When rivers are dammed to create reservoirs, wildlife communities are destroyed. This can necessitate costly wildlife management measures, such as the money currently being used to study threatened blue suckers in the Colorado River. And if already-threatened mussel species were to be further harmed because of reservoirs, water quality benefits could suffer because mussels naturally filter water and remove pollution. Expensive mitigation efforts likely would be required.

4 Reservoirs divert water from Texas rivers; without enough fresh water flowing through rivers into Texas bays to provide essential nutrients, sediments, and salinity moderation, fish and wildlife suffer, harming fishing and tourism-based economies.

5 Over time, sediment builds up in reservoirs, limiting their storage capacity and leading to diminishing returns. Reservoirs greatly increase evaporation rates, which also leads to diminishing returns.

Long-term viability

1 Reservoirs lose massive amounts of water each year to evaporation. As drought and weather patterns become more extreme, we can expect evaporation rates to be even higher. When water evaporates, it is lost to the watershed in large amounts. (While it will fall as rain somewhere else, that may not even be in Texas.)

2 Higher temperatures are becoming increasingly common in Texas, leading to higher water temperatures, less frequent rainfall, and more evaporation, which are resulting in water chemistry changes that make toxic algae blooms more common in reservoirs.

3 Because dams block sediment from traveling downstream through on-channel reservoirs, sedimentation builds up in the reservoirs over time. This can dramatically decrease water storage space, which means that over time these projects either become less useful or must be dredged, which is a time- and cost-heavy process.

4 For a city to use water from a reservoir, the water has to be piped or moved to the city. Because the majority of prime reservoir locations have already been used, reservoirs must be built increasingly far away from the communities they are supplying. If the city is far away and energy costs rise or related carbon emissions become regulated, this strategy could become even more expensive.

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