Surface Water Chapter 9

Surface water movement: Water (Hydrologic) Cycle Earths water supply is constantly recycled

The Water Cycle The Sun provides energy for the water cycle. Radiation from the Sun causes water to change to a gas called water vapor. The process of water vapor changing to a fluid is called condensation.

Precipitation falls to Earth’s surface in the form of rain, snow, sleet, or hail. Water then flows downslope along Earth’s surface which is called Runoff.

Runoff may reach a stream, river, or lake, may evaporate or may accumulate into puddles and eventually seep into the ground.

Water that seeps into the ground becomes groundwater. For water to enter the ground, there has to be large pores or spaces in the ground.

Fate of water: Run off or Seep Certain characteristics will determine whether not water will either seep into or become runoff 1) Vegetation Vegetation allows for loose soil Loose soil allows water to enter ground

Fate of water 2) Rate of precipitation Heavy: Light: Water falls too quickly and becomes runoff Light: allows water to gently slide through

Fate of Water 3) Soil Composition Effects the waters holding capacity Decayed organic matter (humus) Creates the pores in soil which retains water Minerals Clay – fine mineral which clump together Few Spaces Sand – large pores-allows water to move through it.

Fate of Water 4) Slopes Steep: allows for high runoff & little absorption Little: low runoff and high absorption

Formation of Stream systems Precipitation that does not enter the ground usually runs off the surface quickly. Surface water flows in thin sheets and eventually collects in small channels Runoff increases, channels widen and become deeper and longer Channels fill up again each time with rain Channel can become a stream

Streams Some streams flow into lakes and oceans. Tributaries flow into other streams.

Streams A large stream = River. All of it’s tributaries make up a stream or river system. Small streams are called brooks or creeks.

Water sheds (Drainage Basin): Land where all water drains into a stream Divide High land area that separates watersheds

Stream Load All the materials that the stream carries There are 3 ways that a stream carries a load: Solution Suspension Bed Load

Stream Load Solution Material is carried in solution after it becomes dissolved in a stream’s water.

Stream Load Suspension All particles small enough to be held up by the turbulence of a stream’s moving water are carried in suspension. Silt, Clay, Sand

Stream Load Bed Load Large sediments that are too heavy to be held up by turbulent water. Consists of sand, pebbles, and cobbles that the stream rolls and pushes along the bed of the stream.

Stream Load Bed Load As the particles move, they rub, scrape, and grind against one another or against solid rock of the streambed in a process called abrasion. This causes the rocks to be polished and round.

Stream velocity and carrying capacity The ability of a stream to transport material is called the carrying capacity. Discharge = The measure of the volume of stream water that flows over a particular location within a given period of time. Expressed in cubic meters per second (m3/s)

Stream Velocity & Carrying Capacity Discharge = width x depth x velocity (m) (m) (m/s) As discharge increases so does carrying capacity

Floodplains Floods occur when water spills over the sides of a stream’s banks onto the adjacent land. Floodplain: broad flat area of land that extends out from streams for excess flooding

Floods Flood stage = level where a stream overflows its banks and the crest of the stream is at max height Upstream flood = the flooding of a small area. They are localized and cause damage within a short period of time.

Downstream floods Heavy accumulation of excess water from large regional drainage systems. Causes extensive damage.

Flood monitoring and Warnings