Colorado River DeltaSlide 2Slide 3Outline Four Time PeriodsColorado River FactoidsColorado Delta FactoidsSlide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Biodiversity ChangesFuture FocusReferencesSlide 24Colorado River DeltaColorado River DeltaSWES 574SWES 574Fall 2003Fall 2003W.J. WardW.J. WardRodriguez, C. A., Flessa, K. W., Tellez-Duarte, M. A., Dettman, D. L., and Avila-Serrano, G. A.(2001b). "Macrofaunal and isotopic estimates of the former extent of the Colorado River estuary, upper Gulf of California, Mexico." Journal of Arid Environments, 49, 183-193.Outline Four Time Periods Outline Four Time Periods Pre-Hover Dam (late 1800’s to 1932)Pre-Hover Dam (late 1800’s to 1932)Post Hover Dam (1932 to 1996)Post Hover Dam (1932 to 1996)Current focus on Colorado DeltaCurrent focus on Colorado DeltaFutureFutureColorado River FactoidsColorado River FactoidsArea drains over 242,000 square miles on Area drains over 242,000 square miles on its 1,450 mile course its 1,450 mile course Colorado flow rate max 7000 m3s-1 Colorado flow rate max 7000 m3s-1 creating deposits 5 km thick in some areas. creating deposits 5 km thick in some areas. (average annual flow 60 year period (1906-(average annual flow 60 year period (1906-65) is 15.09 million acre-feet 65) is 15.09 million acre-feet Colorado is saltiest carrying 9 million tons Colorado is saltiest carrying 9 million tons per year. Salinities were 32-35 l range now per year. Salinities were 32-35 l range now 35 – 45 l range35 – 45 l rangeFlow irrigates over 1,000,000 acres in the Flow irrigates over 1,000,000 acres in the United States and 500,000 acres in Mexico United States and 500,000 acres in Mexico Source: Worster, 1985, & (Hoover Dam Web Site Hoover Dam Historyhttp://www.usbr.gov/lc/hooverdam/)Colorado Delta FactoidsColorado Delta FactoidsColorado river flowed into the Gulf of Colorado river flowed into the Gulf of California forming a bay 50 miles wide. California forming a bay 50 miles wide. Each year the river deposited 140,000 Each year the river deposited 140,000 acre feet of silt (214 sq. miles coved in 1 acre feet of silt (214 sq. miles coved in 1 ft. of soil) ft. of soil) Colorado Delta was once 3000 sq. miles. Colorado Delta was once 3000 sq. miles. Now ½ that size Now ½ that size The Salton Basin received flow from the The Salton Basin received flow from the Colorado river eight (8) times from 1824 to Colorado river eight (8) times from 1824 to 1904 1904 45 species in the United States segment of 45 species in the United States segment of the Delta are now listed as endangered, the Delta are now listed as endangered, threatened or sensitive threatened or sensitive (Hoover Dam Web Site Hoover Dam Historyhttp://www.usbr.gov/lc/hooverdam/)Aldo Leopold called the Delta “ a vast gallery forest of cottonwood, (Populus fremontii) and willow (Salix gooddingii) in the north interspersed with wetlands containing cattail (Typha domengensis) and common reed (Phragmites australis) in low areas and mesquite bosques (Prosopis glandulosa & Prospis pubescens) in higher terraces”. The endemic salt grass, Distichlis palmeri, dominated the estuarine zone. Beaver, jaguar and deer were in abundance and Egrets flocked in such numbers as to make the ground appear white in 1920.Glenn, E. P., Zamora-Arroyo, F., Nagler, P. L., Briggs, M., Shaw, W., and Flessa, K.(2001). "Ecology and conservation biology of the Colorado River Delta, Mexico." Journal of Arid Environments, 49, 5-15.Typical Colorado Delta Marsh – Early 1900’sColorado river flooded town of Yuma in 1852, 1890, 1905, 1916, 1920. The river port of La Paz was left on high ground in 1868 by the Colorado river changing it’s course. Floods have occurred 1884, 1905, 1909, 1916, 1917, 1923, 1926, 1937, 1939, 1941, 1952, 1957, 1962, 1964, 1965, 1967. 1884 flood was 30.1 million acre-feet with discharge of 300,000 cubic feet per second. Fort Yuma after Railroad Interagency Committee (1970). "Lower Colorado Region Comprehensive Framework Study; app. 9, Flood Control." U. S. Pacific Southwest Inter-Agency Committee, 103.Sykes, 1937, Freshwater fish and saltwater fish at the mouth of the gulf were diminished in numbers as to almost be nonexistent. Bird life and many mammals such as raccoon and beaver were so diminished to have practically disappeared. (Sykes, 1937, The Colorado Delta.Zamora-Arroyo, F., Nagler, P. L., Briggs, M., Radtke, D., Rodriquez, H., Garcia, J., Valdes, C., Huete, A., and Glenn, E. P.(2001). "Regeneration of native trees in response to flood releases from the United States into the delta of the Colorado River, Mexico." Journal of Arid Environments, 49, 49-64.Current Colorado River Flow Today much of the area between channels is a vast monoculture of Tamarix ramosissimaBivalue mollusk Mulinia coloradoensis reduced to only small areas where they can still be found. Total living clams reduced by 95 % due to increased salinity and lower nutrients from sediment flows. Salinities were 32-35 l range now 35 – 45 l range. Rodriguez, C. A., Flessa, K. W., and Dettman, D. L.(2001a)."Effects of Upstream Diversion of Colorado River Water on the Estuarine Bivalve Mollusc Mulinia coloradoensis.“Conservation Biology, 15(1), 249-258 .Changes in downstream water total flows, seasonal timing of flows, short-term fluctuations in flows, extreme high and low flows, & water quality such as temperature, nutrient load, turbidity, and dissolved gases, can dramatically change biodiversity.Biodiversity ChangesBiodiversity ChangesMeander cutting and abandonment of river Meander cutting and abandonment of river channels leads to a geomorphologically channels leads to a geomorphologically diverse floodplain, and consequently the diverse floodplain, and consequently the development of highly complex forest.development of highly complex forest. Channel incision or lowering the channel bed Channel incision or lowering the channel bed causing water table to decline greater than causing water table to decline greater than 1.5 m can greatly impact cottonwood trees.1.5 m can greatly impact cottonwood trees.Populus fremontii survived 1 cm sediment Populus fremontii survived 1 cm sediment deposit by the time it reached 2 cm tall deposit by the time it reached 2 cm tall (approx. 2 weeks); Tamarix ramosissima at (approx. 2 weeks); Tamarix ramosissima at 4-6 cm tall (approx. 5 weeks).