Do Now: What is this picture showing?

A dam…with goats. The Cingino Dam in Italy (169ft tall) is a common place to find the Alpine Goat- they lick the sea salt left from the water

Water Flow  The flow of water is directly effected by weather and seasons Faster flow during and after rain Slower flow during summer when evaporation rates are higher  Water flow has an impact on water quality

Flow and Water Quality  Large, swiftly flowing rivers are less affected by pollution  Small streams will have a larger impact They have less capacity to dilute and degrade wastes.  Flow determines the kinds of organisms that can live in the stream Some need fast-flowing areas; others need quiet pools  Flow affects the amount of silt and sediment carried by the stream. Sediment introduced to slow-flowing streams will settle quickly to the stream bottom. Fast moving streams will keep sediment suspended longer in the water column.  Fast-moving streams generally have higher levels of dissolved oxygen

Changes to Water Flow  Dams, irrigation, droughts and municipal use decrease the water supply which affects water flow  Riparian Zones- unique transition ecosystems between water and land Provides habitats for many different organisms Changing the water flow can increase or decrease the water level which will effect these habitats

Riparian Area

Functions of Riparian Areas  Provides habitats for many organisms Amphibians, insects, birds, mammals  Acts as a buffer for the water Prevents erosion: root systems from plants hold the soil in place Protects against pollution: Vegetation helps to absorb runoff instead of entering the water directly  Provides scenic beauty for recreation areas Fishing, boating, swimming

Dams  Dams have been used throughout history to change water flow for human needs Flood Control Electricity Irrigation Recreation

Oldest Dam: The Quatinah Barrage or Lake Homs Dam, located in Syria The dam was constructed BC, and was expanded in 1934 and Creates Lake Homs, supplying water for the city of Homs through canals. Largest Hydroelectric Dam: Three Gorges Dam in China Spans the Yangtze River *lots of controversy over the construction of this dam* Three Gorges Dam Video

The Good….  Dams allow for flood control  Provides area of recreation which increases economics in an area  Can be used for Hydroelectricity Water behind the dam (reservoir) is let through the dam at specific rates to spin turbines which creates electricity  Reservoirs behind the dam are used for drinking water and irrigation

 Hoover Dam used for Hydroelectricity Dams with spillway for flood control 

The Bad….  Disrupts riparian zones New dams cause flooding upstream and drying downstream  Endangered species of fish Fish cannot migrate Some dams have fish “ladders” to allow them to move through  Water flow is disrupted Reservoirs have higher rates of evaporation Slow flow decreases dilution of pollutants Temperature of water changes (affects DO levels)  Heightened security due to acts of terrorism  Periods of drought have larger effect of reservoir than flowing water

There are 20 dams along the Rio Grande There has been fighting between states and US/Mexico over who controls the water, how much should be let downstream Mexico receives very little of the water and is forced to use expensive methods for irrigation which hurts the economy and sale of their crops

 Water flow slows down abruptly causing: -Low oxygen levels as water slows -Temperature changes -Waste buildup -Sedimentation

Summary  Water flow is a key factor in the water quality for aquatic ecosystems  Dams have many benefits but also cause ecological and economic disruption  Watch the video and use the notes to answer the Ticket Out question: Riparian Areas Video  Ticket Out: What impact would the construction of a new dam have on the riparian areas both upstream and downstream?