June 2015 Stephanie Glenn, Ph.D.
Groundwater is a major source of water worldwide In Texas, 60% of 16.1 million acre-feet of water used annually 61% of groundwater in Texas is used for agriculture 2
Circular connection ◦ River withdrawals can deplete groundwater or pumpage of groundwater can deplete river ◦ Pollution of surface water can degrade groundwater or degraded groundwater can impact surface water quality Need to understand (quantitative) linkages between groundwater and surface water
Recharge, the rate at which water percolates down to the aquifer and “recharges” the water supply varies widely amongst aquifers as well as in an individual aquifer Rates of recharge can be impacted by: ◦ Precipitation changes ◦ Pumping changes ◦ Development on recharge zones ◦ Changes to soil and lens structures
Groundwater-tracer techniques are considered the most reliable estimators of recharge Physical techniques - surface water and unsaturated/saturated zone data provide estimates of potential recharge Modeling provides estimates from published data (precipitation, vegetation, soils, aquifer zones) Recharge rates vary widely amongst aquifers and even within a single aquifer (can vary spatially and temporally) ◦ Gulf Coast from 0.0004 in (.0101 mm) to 2 in (50.8 mm) per year ◦ High Plains from 0.004 (.0101 mm) to 11 in (280 mm) per year ◦ Trinity and Edwards-Trinity Plateau from 0.1 in (2.54 mm) to 2 in (50.8 mm) per year ◦ Seymour from 1 in (25.4 mm) to 2.5 in (63.5 mm) per year Olll i idl f 0 024 i h (0 61 ) i
Distance between the pumping well and the Unhealthy vs. Healthy Lake surface water body Drawdown Rate and duration of pumping Geologic and hydrologic Cone of characteristics of the Depression aquifer Vertical permeability and thickness of the confining beds Difference in head established between the artesian aquifer and the Ground Water Flow in an Aquifer shallow water-table aquifer with a Pumping Well – note that Degree of interconnection pumping has caused water level to between the lake or wetlands bottoms and the decrease under the lake on the left, underlying unconsolidated causing decreased surface water sediments and the limestone
Groundwater adds complication Quantifying interactions ◦ Water withdrawn to irrigate, some water will be lost due to evaporation and use by crops, while some may percolate to the groundwater
Texas Water Plan ◦ Proposed reservoirs are the most Assi Assist sted Ground ndwater expensive items in the Plan Rechar arge ge: $90- ◦ Reservoir permitting and construction $1100 a acre-foot foot are lengthy and contentious Reservoi voir Expans nsion: n: 2011 drought: $1700-$2700 ◦ Evaporation loss from Lakes Travis and acre re-fo foot ot Buchanan > water used by City of Austin Seaw awat ater Desalin linatio ion: Instead of reservoirs $1900-$3000 ◦ ASR: Aquifer Storage & Recovery acre re-fo foot ot (Nu (Numbers rs f fro rom Water security in form of stored Stanford’s W Water r groundwater in th the West) t) Florida has successfully implemented ASR Texas has done so on a smaller scale
Changing Precipitation and Snowmelt patterns: reduced recharge Sea level rise: groundwater recharge by salt water intrusion Reservoir construction changes groundwater recharge patterns ◦ In arid lands, reservoirs often increase recharge right by the reservoir Canals change groundwater recharge patterns Pumping changes groundwater recharge patterns
• USA and Mexico share the Rio Grande/Bravo watershed of 335,000 sq miles • Texas, New Mexico and Colorado share US resources • US – 75% of water is for agriculture • Ongoing litigation between States over rights and usage
During recent drought in the Lower Rio Grande, farmers and urban water managers supplemented decreasing surface water allotments by increasing pumping of groundwater Groundwater is hydrologically connected to the river – borrowing from future water supply Fro rom T The Da Dall llas M Morn rning Ne News: Sa San Angelo S Stat ate Par ark i in 2011 2011 drought
Groundwater pumping used as supplement to surface water, especially in drought ◦ Expensive option (inaccessible for small farmers) ◦ Low flows in river = less recharge ◦ Increased groundwater pumping = lower water levels ◦ Deeper wells draw from levels with higher salinity = decreased farm yields ◦ Impacts on wetlands, riparian vegetation Fro rom: US S Dro Drought M Monit itor, Dro Drought 2 2011
Ogallala – major aquifer in northwest Texas in Rio Grande watershed ◦ Water level changes (n= 25 wells) From 2011 (drought) to 2012 Ranged from 1.2 feet to -10.1 feet Av Average ge c change ge -1.8 f 8 feet From 2012 to 2013 Ranged from 1.8 to -5.2 feet Av Average ge c change ge -1.3 f 3 feet Edwards-Trinity (Plateau) – major aquifer in West Texas in Rio Grande Watershed ◦ Water level changes (n= 21 wells) From 2011 (drought) to 2012 Ranged from 0.8 to -8.7 feet Av Average ge c change ge -2.5 f 5 feet From 2012 to 2013 Ranged from 0.6 to -6.2 feet Av Average ge c change ge -1.2 f 2 feet Alon ong th the Rio o Grande, i ima mage ge c cou ourtesy of of NPS
El Paso and desalination ( Kay Bailey Hutchison Plant) ◦ Desalination has drawbacks Expensive - Plant and infrastructure cost $91 million Waste 20% of water running through it is returned to the ground in brine (extremely salty wastewater) Pumped into 4,000 foot injection wells • Drawdown Pumping brackish water in great quantities runs the risk of fouling freshwater aquifer ◦ Should be studied well prior to use, and monitored regularly Fro rom: Texas T Trib ribune, K KBH Desal al Plan ant A April 2012 2012
New ideas for conservation both in the municipal and agricultural areas will impact water supply ◦ Updates to infrastructure for water utilities and irrigation districts ◦ Incentives ◦ Crop Water Use Efficiency ◦ Diversity of Crop Selection ◦ Water conservation El Paso efforts have resulted in per-person consumption falling by 41% since the Water C r Conserv rvatio ion: D Drip I p Irrig rigatio ion i in a field ld 1970’s El Paso demand in summer 2014 peaked at 160 mgd – close to the Plant’s capacity to pump from the ground
Basin/Groundwater Challenges ◦ Texas, New Mexico, Colorado – Rio Grand Compact Established apportionment for some of the water from the Rio Grande for the three states ◦ U.S. Supreme Court case, Texas v. New Mexico and Colorado (2013) ◦ Texas claims New Mexico is violating the Compact by increased groundwater pumping, reducing flows in the Rio Grande Rio Grande (Nuevo Progresso Bridge, 2007)
May 2015 – Heavy precipitation throughout Texas – 35 trillion gallons Wa Water b r budge get ◦ Popular graphic in the news (texas planning needs ds trib) equated that amount to: to addr address al all Enough to cover all of Texas in 8 inches of water spect ctru rums of Enough to fill up California’s 200 clim climate largest surface reservoirs to 3X capacity Enough to supply the entire world’s sce cenari rios population with 10,000 days of water (eight 8-ounce glasses a day) Drought is “gone”
Percen Per ent capac apacity of monit itore red water wat suppl pply y reserv re rvoirs irs as as o of J June une 2015 2015 From T om Texas W Wate ter Develo lopm pment B Board rd
Too much water from extreme weather events, such as tropical storms. From O om Ocean Nati tion onal Geogr ographic: Seabroo ook p k pos ost- Ike ke Too little water during drought results in wildfires From: m: Huffingt gton on P Post, t, AP P Photo W Wildf ldfire ires i in Te Texas as – Mar arfa, 2011 2011
Resilience should be a complement to Sustainability in planning Resilience is about the ability of the system to survive a major tipping point (severe storms, droughts, climate change) Sustainability assumes constant change and how the system will adapt Best management practices for resilience might not necessarily benefit the sustainability (or vice versa), but should not impede Resilience plans will help understand requirements for sustainability Planning for resilience is key to sustainability
General resilience is the ability of natural and human communities to recover after damaging events Groundwater Resilience often measured in terms of extractable, usable amount of total groundwater storage (How quickly did the aquifer recharge back to normal levels after increased pumping during a drought? Was the water quality impacted?) Watershed resilience needs to be a goal for SERIDAS ◦ Ability of entire watershed (surface water, groundwater and interconnections) to recover after slow-burn (drought) and swift (extreme rainfall) impacts • Resilience = better human health, sustainable environment, and robust economy
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