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Managing Interbasin Water Transfers
to Achieve No Net Loss
Sustainability: This is a term used to describe whether water will continue to be available from a particular source. In surface water, limitations on sustainability may be determined by drought, reduced inflow to a reservoir from upstream sources, or demands increasing beyond the sustainable capacity of the source. In groundwater, sustainability may be affected by demand on the aquifer, recharge rates, and natural discharge through springs. Sustainability of a water resource is ensured by protecting the inflow from contributing watersheds, protecting recharge areas, and by limiting demands.
Reliability: This describes the probability that water will be provided from this alternative. It is used to estimate how frequently conditions – either environmental or caused by people’s actions – will arise where the water will not be available.
Equity: A term used to indicate whether something or someone gains while something or someone loses.
Benefits: Advantage, profit, good. One benefit would be volume of water produced by an alternative that is currently not available from a source. Additional benefits may include: improved environmental quality, increased reliability of water available to users, continued economic development in an area, or other benefits.
Risk: A measure in terms of probability of the factors that could undermine the success of the alternative. In some alternatives, the ability to obtain a permit for the alternative presents a risk that results from environmental or other impacts.
Indirect costs: In costing the alternatives, it is LCRA’s administrative costs related to implementation and monitoring of the water replacement strategy.
404 permit: Section 404 of the Clean Water Act requires permits for the discharge of dredge or fill material into waters of the United States, including wetlands. Almost any construction that involves a reservoir, river, or creek requires a 404 permit.
Firm, non-interruptible water: The volume of water expected by the supplier to be available at all times except for reasons of uncontrollable forces. For a reservoir, it is the volume that the reservoir can supply through the most severe drought ever recorded in a particular area.
SCADA system: An electronic Supervisory Control and Data Acquisition system that monitors water levels between check structures in the canal system. Based on predetermined water levels or flow conditions, the SCADA system relays control information (start and stop) to the pump stations and to automated check structures that are adjusted to regulate flow. For example if demand is reduced and the water level starts to increase in a section of the canal system, the SCADA system would signal the check structure to close slightly to restrict flow into that section. When the next section of canal upstream is the pump station, the SCADA system signals the pumps to turn off. An opposite sequence would apply if demand is increasing and water level in the canals begins to decline.
Water table: The level of groundwater or height to which water will rise in a well when the well is not operating.
Drought conditions:
The two water storage lakes, Travis & Buchanan, depend on rainfall, inflow from tributaries, and inflow from the upstream arm of the Colorado for replenishment. When no significant amount of rain falls in the Colorado River watershed, flow into the lakes can become extremely low.
Every spring and summer LCRA increases the amount of water released from the lakes to satisfy increasing downstream needs, such as drinking water in Austin, irrigation for farming, and fresh water for fish and other aquatic life.
“Bed and banks” transfer: A specific provision in the Texas Water Code that allows use of the bed and banks of a stream to transport water from one location to another. Usually, the amount that can be withdrawn from the downstream location is reduced from the amount placed in the stream to allow for evaporation and seepage losses. Usually, water returned to a stream after use by a water rights holder is considered to revert to state ownership.
Total dissolved solids (TDS): The total weight of the solids that are dissolved in the water, given in parts per million (ppm) per unit volume of water. Usually used to describe the amount of dissolved minerals or salts in water.
Drawdown: The drop in the water table or level of water in the ground when water is being pumped from a well, or resulting from a period of pumping in an area.
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