Climate Change Impacts on Hydropower in the River Basin

KEY MESSAGE: Climate change has the potential to reduce hydropower production in the Rio Grande Basin through decreases in streamflow, increases in temperature, and increases in evaporation rates. Poli- cy makers need to act quickly and effectively to implement the development of sustainable energy alterna- tives, encourage conservation and efficiency, and construct hydropower plants at existing sites.

he Rio Grande is an essential freshwater source for over 13 million people living in northern and the southwestern U.S. (USCB 2013, CONAPO 2013). At T1,896 mi (3,051 km) long, the Rio Grande is the fifth longest river in North America and the twenti- eth longest river in the world. Starting at the head- waters in the San Juan Mountains of southern Colo- rado, the Rio Grande flows southward through , , and Mexico where it empties into the . The Rio Grande flows 1,255 mi (2,019 km) along the U.S. Mexico border, splitting the river’s 182,000 mi2 (471,000 km2) drainage ba- sin nearly equally between the two countries (IBWC 2014).

Hydropower in the Rio Grande River Basin

There are 21 major and diversion located along the Rio Grande (Figure 1), eight of which are Figure 1. Dams and diversions located on the Rio Grande. Source: used for hydropower generation (Kao et al. 2014). Bullard & Wells 1992. Currently, the Rio Grande Basin has 159 megawatts (MW) of hydropower capacity and generates 312,000 meg- Texas and the State of , Mexico, is the next largest awatt hours (MWh) of electricity annually (Kao et al. hydropower dam on the Rio Grande (TWDB 2014a). It 2014), which is enough to support approximately 29,000 contains two power plants, one generating power for each U.S. households (USEIA 2012). country, and is managed by the International Boundary and The largest hydropower dam by size on the Rio Grande Water Commission. Combined, the power plants generate is the , located in Truth or Consequenc- approximately 161,000 MWh annually (IBWC 1990). The es, New Mexico. Completed in 1912, the Elephant Butte storage capacity of the Amistad International is Dam is a major component of the , a 3.3 million acre-feet (4.1 km3) (TWDB 2014a). series of dams, drainage channels, and on the Upper Another major hydropower plant located on the Rio Rio focused on , hydroelectric, and Grande is the , which is located between Starr interbasin water transfer (USBR 2009). Collecting water County, Texas and in Mexico. from a catchment of 28,900 mi2 (74,900 km2), which is Completed in 1945, the Falcon Dam has an installed capac- about 16 percent of the total , the Elephant ity of 63 MW (IBWC 1990). The Falcon International Res- Butte reservoir is capable of storing over 2 million acre-feet ervoir has a storage capacity of 2.6 maf (TWDB 2014b). (2.5 km3) of water (USBR 2009). The Elephant Butte hy- While relatively little hydropower is currently generat- dropower plant has a capacity of 27.95 MW and is able to ed in the Rio Grande Basin, there is great potential for in- generate 56,003 MWh of electricity annually (USBR 2009). creased development. It is estimated that the total undevel- The electricity generated at Elephant Butte is distributed oped hydropower capacity of the Rio Grande is 1.64 giga- through an totaling 490 mi (788.6 km) of 115 watts (GW), which is ten times more than is currently in- kilovolt transmissions lines and 11 substations (USBR stalled (Kao et al. 2014). Such capacity could generate 9.31 2009). terawatt hours (TWh) of electricity per year, nearly 30 The , which straddles Val Verde County, times current generation rates (Kao et al. 2014). These fig- ures take into account only U.S. streams, there- fore the undeveloped hydropower in the entire basin, including Mexico, could be greater. Hydropower development has not been the main priority in the Rio Grande Basin. The Rio Grande’s semi-arid climate has created a region focused primarily on water resources for agri- culture and municipal. The majority of the water used in the Rio Grande is used for agriculture and municipal purposes, supplying more than 6 million people with drinking water and 2 mil- lion acres (800,000 hectares) of land with irriga- tion water (IBWC 2014). Agriculture and urban landscaping will require more water with the anticipated increase in temperature (Llewellyn & Vaddey 2013). Growing populations in U.S. Figure 2. Decrease in the flow into the under and Mexican urban centers will increase munici-baseline conditions and under full delivery with management strategies pal demands. To reconcile increased demand utilized to meet allocation requirements. Source: Llewellyn & Vaddey with decreased supply, there will likely be a 2013. shift from using the Rio Grande’s surface water to non-renewable groundwater. The new dependence on nitude, timing, and spatial distribution of stream flow, due groundwater will lead to over-extraction, resulting in lower to the fact the Rio is mostly snow fed (Llewellyn & Vaddey water availability in the Rio Grande due to the lack of base 2013). Mean annual runoff is predicted to decrease by 7.3- flow from surrounding aquifers and tributaries (Llewellyn 14.4 percent by 2050 (USBR 2011), which will decrease & Vaddey 2013). inflows into (Figure 2). Peak flow from the river’s headwaters in is predicted to arrive in May Climate Change in the Rio Grande River Basin instead of June, and overall flow will decrease between June and September (Llewellyn & Vaddey 2013). Some Climate change is projected to decrease water availabil- studies estimate that climate change could reduce Rio ity, change peak flow periods, increase extreme weather Grande flows by 4-14 percent by 2030 and 8-28 percent by events, alter precipitation patterns, and increase temperature 2080 (Hurd & Coonrod 2008).This combination of changes in the Rio Grande Basin. During the period 1971-2011, the will lead to an overall decrease in water availability. average temperature in the Upper Rio Grande Basin in- creased roughly 0.7° F (0.4° C) per decade, approximately Climate Change Impacts on the Energy Sector double the global rate of temperature rise during this time (Llewellyn & Vaddey 2013). Climate studies utilizing nu- Lower streamflow will impact the productivity of hy- merous general circulation models and future atmospheric dropower dams in the Rio Grande basin. Overall, lower carbon dioxide scenarios predict there will be a 4.0-6.0° F streamflows will lead to lower reservoir levels (Llewellyn (2.2-3.3° C) increase in the upper basin by the end of the & Vaddey 2013), resulting in decreased in hydropower 21st century (Llewellyn & Vaddey 2013). Furthermore, pre- generation (Figure 3). Decreases in water level have al- cipitation is forecast to decrease by 2.3-2.5 percent by ready been observed in reservoirs along the Rio Grande. 2050, and variability in the magnitude and timing of precip- During the main irrigation season of 2012, reservoir levels itation is predicted to increase (USBR 2011). were observed dropping by 2.5 feet per day (0.76 meters An increase in temperature and changes in the precipi- per day) (Guido 2012). In the Upper Rio Grande basin there tation patterns may have a variety of effects on streamflow is 15 MW of hydropower capacity available, but this is pre- in the Rio Grande Basin. Currently, water lost through dicted to decrease by nearly 50 percent by the end of the evaporation in this semi-arid to arid climate exceeds the 21st century (Llewellyn & Vaddey 2013). Most of this de- water gained by precipitation, a disparity that will only crease will likely occur between May and September, the grow larger as evaporation rates increase and precipitation same months in which streamflow is predicted to decrease. rates decrease (Patina et al. 2005). Additionally, predicted Potential increases in evaporation rates from open reser- earlier dates of snowmelt will lead to variability in the mag- voirs may also impact hydropower generation (Figure 4), yet the volume of water lost Grande’s location in a arid could decrease over time to semi-arid region makes because less water surface solar energy a viable alter- is exposed to air as reser- native. In Culberson Coun- voir levels decrease. ty, Texas, located northeast Decreases in hydropow- of the Rio Grande, there are er generation are predicted two wind farms utilizing to coincide with increasing 147 turbines with a 68 MW energy demand as popula- capacity, enough to power tions grow in the Rio 15,650 average Texas Grande Basin. Over the last homes (American Wind En- 40 years, the population of ergy Association 2008). Pol- the border communities has icies should focus on the doubled every 20 years, and promotion of alternative it is predicted to double energy sources which do not again by 2030 (Schmandt rely on the availability of 2002). Region M of the Rio water in the Rio Grande or Grande, which includes Figure 3. The predicted hydropower generation in the Upper the burning of fossil fuels. eight counties of Texas, is Rio Grande basin. Shows three major hydropower dams. In order to maintain the expected to grow from 1.7 Source: Llewellyn & Vaddey 2013. current hydroelectric pro- million in 2010 to 4 million duction in the Rio Grande in 2060, increasing water demand by 35 percent (RGRWA Basin, polices which protect streamflow and increase water 2010). Current hydropower capacity in the basin will be levels in reservoirs must be implemented. Overall, conser- unable to address the basin’s growing energy needs. vation and efficiency in agricultural and municipal water use will be needed to continue hydropower production. As Policy Implications stated before, agriculture and municipalities use the majori- ty of water in the Rio Grande basin. Programs promoting The Rio Grande is managed by the International efficient irrigation techniques and water efficient crops will Boundary and Water Commission (IBWC), which is re- lead to a decrease in water use by farmers. Additionally, sponsible for water distribution, conservation, and imple- water-sharing programs, in which farmers sell water rights mentation of treaties and agreements. The Convention of to municipalities, will lead to an reduction in water loss due 1906 allocates the waters from El Paso to Fort Quitman to the fact that crops will not be grown in high evaporation along 89 mi (143 km) of the international border. The Ele- areas. Aggressive conservation and efficiency will be need- phant Butte Dam, funded by the U.S., was constructed to ed to increase streamflow and continue the production of meet the allocation of 60,000 acre-feet of water to Mexico hydropower. annually (Umoff 2008). The Water Treaty of 1944 ad- The construction of more hydropower dams has been dressed the utilization of the waters in the Colorado and the proposed in order to increase the energy production in the Rio Grande from Fort Quitman, Texas to the Gulf of Mexi- Rio Grande since there is a high amount of potential hydro- co (Umoff 2008). The Treaty of 1944 states that hydroelec- power. However, streams located in national parks and the tric dams be built at international storage dams specified in presence of critical habitats and species make the construc- the Treaty, funded by the U.S. and Mexico, and operated tion of hydropower dams a difficult task. There are 79 na- and maintained by the Section engineer of each country. tive species in the region, 11 of which are protected under Climate change will impact the ability of the U.S. to deliver the Endangered Species Act and 14 of which are listed un- Mexico’s allotment of water, especially as the level in the der the International Union for Conservation of Nature Elephant Butte Reservoir decreases. (Kao et al. 2014). Seventy-two percent of stream reaches To address the energy deficit created by increasing de- with potential for development of hydropower have one to mand and decreasing hydropower capacity, policymakers two fish species falling under the ESA (Kao et al. 2014). must support the development of sustainable energy alter- Constructing new hydropower dams along the Rio Grande natives. Overall, there is a strong potential for alternative without harming sensitive habitats seems unlikely. If new energy sources, wind, solar, and geothermal in the basin hydropower plants are planned, they should be constructed (American Wind Energy Association 2008). The Rio at existing dam sites along the Rio Grande, instead of at new locations. Policies which only allow the construction of hydropower plants at existing dams may decrease the risk of harming endangered species further. In conclusion, climate change is predicted to have neg- ative impacts on hydropower in the Rio Grande Basin. With predicted increases in temperature, decreases in precipita- tion, and increases in evaporation rates, streamflows and reservoir levels are anticipated to decrease in the basin, re- ducing hydropower production. Policies must focus on the efficiency of water use, promote water conservation, inves- tigate the potential alternative energy sources, and encour- age construction of hydropower plants at existing dams.

-Authored by Victoria Lubner; Edited by Will Kort & Aa- Figure 4. Open-water evaporation rates at the Elephant Butte ron Thiel; Supervised by Dr. Jenny Kehl Reservoir. Source: Llewellyn & Vaddey 2013.

References

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