Global Reach of Dams and Reservoirs David Rosenberg CEE 6490 – Integrated River Basin / Watershed Planning & Management

Learning Objectives Inventory global and US distributions of dams Recognize time periods when dam building occurred Demonstrate hydrologic, economic, and human impacts of dams

Distribution of large reservoirs 633 large reservoirs (Vorosmarty et al., 2003)

Gross figures of existing dams on Earth 45,000 dams are at least 15 m tall They retain > 6500 km3 of water 5.3 Billion AF 15% of total global runoff 300 giant dams (> 150 m tall; >15 x 106 m3 dam volume; or, > 25 km3 storage) Three Gorges Dam is largest dam on Earth 181 m tall Stores > 39 km3 of water (32 MAF)

Degree of flow regulation Ratio = reservoir storage / mean annual flow Greatest flow regulation -- Volta (Africa) = 4.28) Other significant regulation Manicougan > 2.50 Colorado > 2.50 Rio Negro (Argentina) = 1.40 Euphrates-Tigris = 1.24 Mae Khlong (Thailand) = 1.30 (Nilsson et al., 2005)

Dam Databases ICOLD and IWPDC (worldwide registers of dams) All dams > 15 m but many incomplete parts ~746 reservoirs with >0.5 km3 storage Worldwide geographic data bases UNESCO discharge data and runoff models

http://www.agc.army.mil/Media/FactSheets/FactSheetArticleView/tabid/11913/Article/480923/national-inventory-of-dams.aspx

What is in the NID? All dams Data collected by USACE and FEMA > 6 ft (2 m) tall with > 50 af (61,700 m3) storage > 25 ft (8 m) tall with >15 af (18,500 m3) storage that pose a “significant downstream threat” Data collected by USACE and FEMA Errors up to 4%

NID Findings 75,187 dams in U.S. All watersheds larger than 2000 km2 have dams Most dams are small A few large dams store most surface water (Graf, 1999)

NID Findings (cont.) Northeast has greatest dam density (0.015 dams/km2) Texas Gulf has greatest watershed fragmentation Rio Grande and Lower Colorado most disrupt water and sediment fluxes (Graf, 1999)

NID Results (cont.) Rio Grande and Lower Colorado have highest cost to supply additional water California and Lower Colorado have many people and few dams Lower Colorado has large reservoirs in relation to population (Graf, 1999)

Reservoir construction over time in the U.S. 18,833 dams with 230 MAF of storage built in 1960s (Graf, 1999)

Capacity expansion by region Gradual increases Accelerated periods of construction Hoover Dam Glen Canyon Dam (Graf, 1999)

Research Activity Questions: Is a country’s economic productivity correlated to water storage capacity in dams? How has water storage capacity changed with time for different countries?

Research Activity Question 1: Is a country’s economic productivity correlated to water storage capacity in dams?

Research Activity Question 1: Is a country’s economic productivity correlated to water storage capacity in dams? Part 1, Individual Tasks: Choose country and enter name into GoogleSheet: http://tinyurl.com/jdxbz7h Visit FAO Aquastat: http://www.fao.org/nr/water/aquastat/data/query/index.html?lang=en Find the GDP per capita and Dam Capacity per capita for your country for the most recently available time Enter values into GoogleSheet

Research Activity Question 2: How has water storage capacity changed with time for different countries? Part 2, Individual Tasks: For same country as part 1, use data from FAO Aquastat: http://www.fao.org/nr/water/aquastat/data/query/index.html?lang=en Find the total Dam Capacity (km3) for your country for all times available Enter values into GoogleSheet

Impacts Altered flow regimes Sediment trapping Watershed fragmentation Flood frequency and duration Mean annual flow Base (minimum) flows Sediment trapping Watershed fragmentation Economic Human

Nile River Discharge below the High Aswan Dam, Egypt (Vorosmarty and Sahagian, 2000)

Colorado River below Glen Canyon Dam

Flow-Duration below Glen Canyon Dam Pre-Dam (1921 – 1963) Post-Dam (1963 – 2000)

Lower Colorado River Flow at Yuma

Indicators of Hydrologic Alteration Magnitude of monthly water conditions Magnitude and duration of annual water conditions Timing of annual extreme water conditions Frequency and duration of high and low pulses Rate and frequency of water condition changes (Richter et al., 1996)

Sediment Trapping by Large Reservoirs (Vorosmarty et al., 2003)

Watershed Fragmentation 292 large river systems (LRS) Basins with a virgin mean annual discharge (VMAD) > 350 m3/s (~12,000 ft3/s) VMAD = most water-rich channel section Drain 54% of world’s land mass Fragmentation index: Mainstem: 5 classes ~ longest main channel length without dams / entire main channel length Tributaries: 3 classes (no dams, dams only on minor tribs, dams on major tribs) (Nilsson et al., 2005)

Un-impacted Moderately impacted Strongly impacted (Nilsson et al., 2005)

Human impacts 40 – 80 million people displaced Millions more downstream suffer serious harm Disproportionate impacts on indigenous & tribal people & ethnic minorities (WCD, 2000)

Conclusions Inventory global and US distributions of dams Recognize time periods when dam building occurred Demonstrate hydrologic, economic, and human impacts of dams

References Dynesius, M., and Nilsson, C. 1994. Fragmentation and flow regulation of river systems in the northern third of the world. Science 226: 753-762. Collier, M. J., Webb, R. H., and Schmidt, J. C., 1996, Dams and rivers, primer on the downstream effects of dams: U.S. Geological Survey Circular 1126, 94 p. Rosenberg, D., McCully, P., Pringle, C. 2000. Global-Scale Environmental Effects of Hydrological Alterations: Introduction BioScience 50(9):746-751. Vorosmarty, C. J., Sharma, K. P., Fekete, B. M., Copeland, A. H., Holden, J., Marble, J., and Lough, J. A. 1997. The storage and aging of continental runoff in large reservoir systems of the world. Ambio 26 (4): 210-219.

References (cont.) Vorosmarty, C. J., and Sahagian, D., 2000. Anthropogenic Disturbance of the Terrestrial Water Cycle. BioScience 50(9):753-765. Graf, W. L. 1999. Dam nation: a geographic census of American dams and their large-scale hydrologic impacts. Water Resources Research 35 (4): 1305-1311. Vorosmarty, C. J., Meybeck, M., Fekete, B., Sharma, K., Green, P., and Syvitski, J. P. M. 2003. Anthropogenic sediment retention: major global impact from registered river impoundments. Global and Planetary Change 39(1-2): 169-190. Nilsson, C., Reidy, C. A., Dynesius, M., and Revenga, C. 2005. Fragmentation and flow regulation of the world’s large river systems. Science 308: 405-408.