Water Cycle, Groundwater, Aquifers, Caves Hydrosphere Water Cycle, Groundwater, Aquifers, Caves

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 involved in the cycle include: Precipitation Evaporation Infiltration - the movement of surface water into rock or soil through cracks and pore spaces Runoff - Excess water that flows into streams, rivers, and the ocean. Transpiration - the release of water into the atmosphere from plants through the ground

Poorly sorted sediments Precipitation and Groundwater Runoff is water flowing downslope along Earth’s surface. Runoff may reach a stream, river, or lake, and eventually seep into the ground. The rain can also infiltrate the ground and become groundwater. Little precipitation becomes runoff and is returned to the ocean. Porosity is the percentage of pore space in a material. Well sorted sediments High porosity Poorly sorted sediments Low porosity

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

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

Wells To produce water, a well must tap into an aquifer. 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 Overpumping of a well produces a cone of depression around the well. 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.

Confined Aquifers 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.

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 The overpumping 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 Pollution in Groundwater

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.

Runoff Runoff is water flowing downslope along Earth’s surface. Runoff may reach a stream, river, or lake, may evaporate or accumulate and eventually seep into the ground.

Stream Basics A stream is a channel with permanent water flow. A river is a large stream. Smaller streams that add to an existing larger streams are called tributaries.

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

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.

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.

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

Meandering Streams 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.

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.

Deposition of Sediments 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.

River Basin A river basin is all the land in which water flows on or under into a major river. All of a river basin’s water ends up in one central river that heads towards an estuary or ocean.

Watershed A watershed is a smaller area of land that drains into a wetland, lake, or small stream. Several watersheds make up a river basin.

Pollution within Watersheds Areas downstream, closest to the ocean, are susceptible to all pollutants that have passed through the river basin up to that point, affecting the water quality for coastal inhabitants. Where would the purest samples of water in NC be found?