Water Cycle, Groundwater, & Surface water HYDROSPHERE Water Cycle, Groundwater, & Surface water

Hydrosphere About 97 % of the hydrosphere is in the oceans. Water contained by landmasses—nearly all of it freshwater—makes up about 3 %

Hydrosphere

Water Cycle Water constantly moves among the oceans, the atmosphere, the solid Earth, and the biosphere. This unending circulation of Earth’s water supply is the water cycle.

Water Cycle Processes Evaporation - water from Earth is changed to gaseous state and enters the atmosphere. Condensation - water vapor in the air turning into liquid water. Precipitation - water falling to Earth as rain, snow, sleet, or hail.

Water Cycle Processes cont. Infiltration - the movement of surface water into rock or soil through cracks and pore spaces. Transpiration - the release of water into the atmosphere from plants through the ground. Runoff - excess water that does not permeate into the land and flows over the surface instead.

Water Cycle Processes cont. Sublimation - the conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage. Percolation - the movement of water through fractures or interstices of a rock or soil.

Water Cycle solar energy source condensation

Water Cycle Balance in the water cycle means the average annual precipitation over Earth equals the amount of water that evaporates.

Surface Water Runoff is excess water that does not permeate into the land and flows over the surface instead. Runoff may reach a stream, river, or lake, may evaporate or accumulate and eventually seep into the ground.

Surface Water Runoff Vegetation – reduces runoff by allowing more water to enter the ground Precipitation – light, gentle rainfall causes less runoff than a torrential downpours. Soil Composition – high runoff if soil consist of silt, clay or shale, low runoff if soil consist of gravel or sand Slope of the land – steep slope = high runoff, shallow slope = low runoff

Surface Water Stream Systems A stream is a channel with permanent water flow. Tributaries are streams that flow into other streams, increasing the size of the stream it is joining. A large stream is called a river, and all its tributaries make up a stream, or river system.

Surface Water Rivers Flow of a river or stream is due to GRAVITY. Discharge is the speed at which a river flows (volume rate of water flow; or how much water is passing by). The following formula is used to calculate the discharge of a stream: discharge  = width  X  depth  X  velocity (m3/s) (m) (m) (m/s)

Surface Water Moving Water Carves a Path Stream banks are the ground bordering the stream on each side A stream channel forms as the moving water erodes a narrow pathway into rock, creating sediment.

Surface Water Formation of Stream Valleys As a stream actively erodes its path through the sediment or rock, a V-shaped channel develops. A stream erodes until its base level, the elevation at which it enters another stream or body of water.

Surface Water Stream Load A stream carries its load in 3 ways: Solution - particles dissolved in water Suspension - particles small enough to stay afloat in water. Bed load - materials that are pushed along bottom of stream

Surface Water Meandering Streams A stream’s slope, or gradient, decreases as it nears its base level. Sometimes, the water begins to erode the sides of the channel in such a way that the overall path of the stream starts to bend or wind. A meander is a bend or curve in a stream channel caused by moving water.

Surface Water Meandering Streams cont. Outside of curve-heavy erosion occurs, water moves fastest. Inside of curve-deposition occurs, water moves slowest

Surface Water Meandering Streams cont. It is common for a stream to cut off a meander and once again flow along a straighter path. The cut off meander becomes an oxbow lake, which eventually dries up. At the mouth of the stream, the gradient begins to flatten and the channel becomes wide.

Surface Water Deposition of Sediments Gradient (slope) decreases, velocity decreases. In dry regions, a stream’s gradient may suddenly decrease causing the stream to drop its sediment at the base of a slope as a fan-shaped deposit called an alluvial fan.

Surface Water Deposition of Sediments cont. Streams lose velocity when they join larger bodies of quiet water. A delta is the triangular deposit, usually consisting of silt and clay particles, that forms where a stream enters a large body of water.

Nile Delta

Surface Water and Ground Water Groundwater and surface water have a reciprocal relationship, regularly feeding each other. Most streams and rivers get about half their volume from groundwater. Source: The Water Connection

Estuaries and Wetlands -An estuary is the area in which one or more rivers enter into the ocean, creating brackish water. -A wetland is any area, for at least part of the year, in which the soil is completely saturated or covered with a shallow layer of water. -Area surrounding estuaries is typically going to be wetland.

Reasons to Preserve Estuaries Economic resource-tourism, fisheries Biologically diverse-densely populated Center for many species’ reproduction

Reasons to Preserve Wetlands Wetlands naturally filter pollutants Can withstand excessive amounts of runoff, preventing flooding Plants assist in stabilizing shorelines

Watershed/Drainage Basin A watershed or drainage basin is the land area that contributes water to a stream. A divide is an imaginary line that separates the drainage basins of one stream from another.

NC Drainage Basin Raleigh

Watershed/Drainage Basin

Precipitation & Groundwater Little precipitation becomes runoff and is returned to the ocean. The rain infiltrates the ground and becomes groundwater. Porosity is the percentage of pore space in a material. Well sorted sediments High porosity Poorly sorted sediments Low porosity

Groundwater Movement Groundwater moves by twisting and turning through interconnected small openings. The groundwater moves more slowly when the pore spaces are smaller. http://techalive.mtu.edu/meec/module01/Infiltration2.html

Groundwater Movement Groundwater flows downhill in the direction of the slope of the water table. Permeability is the ability of a material to let water pass through it. High permeability-large, connected pores Ex sand, gravel Low permeability-tiny pores, fine grained materials, said to be impermeable Ex silt, clay, shale

Groundwater Movement

Groundwater Area above water table is known as zone of aeration, pores filled with air. The water table is the upper boundary of the zone of saturation. The zone of saturation is the depth below Earth’s surface at which groundwater completely fills all the pores of a material.

Groundwater The topography of the water table follows the topography of the land above it. Because of its dependence on precipitation, the water table fluctuates with seasonal and other weather conditions.

Groundwater Aquifers are underwater permeable layers where most groundwater flow takes place. Impermeable layers, called aquicludes, are barriers to groundwater flow.

Groundwater Water-table aquifers are unconfined and unprotected, and thus, easily polluted. Deeper aquifers, called confined aquifers, are sandwiched between aquicludes. The aquicludes form barriers that prevent pollutants from reaching such aquifers

Aquifers of NC

Wells Wells are holes dug or drilled deep into the ground to reach a reservoir of groundwater. To produce water, a well must tap into an aquifer

Wells Drawdown is the difference between the original water-table level and the water level in the pumped well. Recharge is the process in which water from precipitation and runoff is added back to the zone of saturation Over-pumping of a well produces a cone of depression around the well.

Wells

Threats to Our Water Supply Human demands for freshwater include household use, agriculture, and industry.

Threats to Our Water Supply Overuse As human population increases, so does the need for abundant water. If groundwater is pumped out at a rate greater than the recharge rate, the groundwater supply will inevitably decrease, and the water table will drop.

Threats to Our Water Supply Subsidence Ground subsidence, or the sinking of land, is a problem caused by the excessive withdrawal of groundwater.

Threats to Our Water Supply Salt Contamination The over-pumping of wells near the ocean can cause the underlying salt water to rise into the wells and contaminate the freshwater aquifer.

Threats to Our Water Supply Septic Waste Contamination

Threats to Our Water Supply *Point Source Pollution: comes from a single, localized source EX: factory

Threats to Our Water Supply *Nonpoint source pollution - pollution from a general area Ex: runoff from farming area

Protecting Our Water Supply All major pollution sources need to be identified and eliminated.

Protecting Our Water Supply Pollution plumes may be stopped by the building of impermeable underground barriers. Polluted groundwater can be pumped out for chemical treatment on the surface.