Transcript Document
Texas Springs: leaking into an uncertain future Chad Norris Water Resources Branch [email protected] (512) 389-8761 GROUNDWATER • Supplied 59% of water used in TX in 2003 • Population expected to double by 2060 • GW level declines predicted for many aquifers over next 50 years (TWDB 2007) • Impacts to groundwater dependent habitats (e.g. springs) unclear San Antonio Springs What is a Spring? • The natural flow of groundwater to the land surface or a surface water body • Artesian or gravity • Ephemeral, intermittent, or perennial • May form marshes, ponds, or streams • A springs characteristics is largely determined by hydrogeologic setting Edwards Plateau Springs Edwards-Trinity (Plateau) Aquifer Texas Springs • Major and Historical Springs of Texas (TWDB Report 189) • Documented loss and decline of Tx Springs • 65 of 281 (23%) springs no longer flowed • Only 2 of 4 largest springs remained Texas Springs • Springs of Texas Vol. 1, 1981 – Gunnar Brune • Describes about 2,000 springs from 183 TX counties • Further documented loss and decline of TX springs United States Geological Survey Springs (Heitmuller and Reece 2004) Gillespie Kerr Real Bandera Importance of Springs • Recognized as valuable ecological, natural, and cultural resources • Barometer of local hydrologic conditions and watershed health • Generally a source of high quality water – increases assimilative capacity Importance of Springs • Water source for local wildlife – Often only perennial water source • Significant component of natural flow regime in many streams – “baseflows” • Unique aquatic habitats that often sustain high degree of diversity Springs - Natural Flow Regime • Often compose significant portion of streamflow – especially in arid west • Provide baseflows to streams and rivers – Sustain aquatic and riparian habitats during drought - perennial vs. intermittent – Historically reliable water supply – Primary source of recharge during drought – Affects property values Gaining vs. Losing Streams Gaining Stream Losing Stream Springs - Natural Flow Regime • Kansas rainfall 15-20 in/yr in West and 40-45 in East • GW use from High Plains Aquifer in west is high • Gaining streams turned to losing streams (Sophocleous and Wilson 2000) Springs - Unique Aquatic Habitats • Transition between groundwater and surface water habitats – “Ecotone” • Thermally and hydrologically stable habitats • Commonly harbour rare, endemic, or relict species • Provide refuge for common species Spring-dependent Fish Plateau shiner – Cyprinella lepida Greenthroat darter (Etheostoma lepidum) Common Fish Species Central Stoneroller (Campostoma anomalum) Longear sunfish (Lepomis megalotis) Green sunfish (Lepomis cyanellus) Mexican tetra (Astyanax mexicanus) Damselflies & Dragonflies Mayflies Beetles Aquatic Macroinvertebrates Crustaceans of Springs Caddisflies True Bugs Snails Conservation Issues • Majority of Springs on Private Property – Recharge features and flow system rarely on same property • Sustainable use of aquifers • Texas water law does not adequately address GW/SW interactions – GW – Rule of Capture; GCD’s, GMA’s – SW – Prior appropriation Conservation Issues How can we conserve springs? • Identify springs and gather baseline data • More hydrogeologic information needed – Identify major outlets of aquifers and associated recharge features, flow paths, and residence times • Address connected nature of GW and SW – Require large-scale GW pumping to assess impacts on springs and SW • Holistic watershed management • Outreach and education Texas Springs: leaking into an uncertain future Chad Norris Water Resources Branch [email protected]