Freshwater

The Water Cycle

Topographic Maps Topography The surface features of the Earth Determines where water will collect in streams, rivers, ponds, and lakes

Topographic Maps A type of map which shows a region’s topography Show both natural features, such as rivers and hills, and constructed features, such as roads and buildings

Topographic Maps Contour Lines connect points on a map that have the same elevation compared to sea level Contour Intervals refer to the change in elevation between one contour line and the next one

Topographic Maps The spacing and direction of the contour lines will help you determine the shape of the land The closer the lines, the steeper the slope A V-shape usually indicates a stream or river, with the V pointing upstream Contour lines with hash marks indicate a depression

Freshwater If more precipitation falls than is absorbed by plants or the ground, runoff occurs. The water collects in the lowest regions in either streams, rivers, ponds, or lakes.

So what exactly is the difference between a pond and a lake? Freshwater So what exactly is the difference between a pond and a lake?

Freshwater A pond is just a small lake in which enough sunlight reaches the bottom to support plant growth

River Systems A river system is made up of a main stream and all the feeder streams, called tributaries. Watershed, or drainage basin, is the land where all runoff enters the same river system.

River Systems Watersheds are separated by ridges or elevated regions of high ground called divides

River Systems As runoff moves across the land, it erodes the surface into a narrow ditch called a gully Continued precipitation, erosion, and widening of the gully leads to a permanent stream

River Systems Channel- the path that a stream follows The stream carries more than just water as it flows- soil, loose rock, dissolved minerals All of the materials carried by a steam are the stream load

River Systems Suspended Load- fine sand and silt that does not sink to the stream bed Bed Load- coarse sand, gravel, and pebbles that grind at the stream bed as they are carried downstream Dissolved Load- minerals that are dissolved in the water

River Systems Erosion is also affected by a streams discharge and velocity Discharge- the volume of water carried by a stream in a given amount of time Velocity- the speed the water flows

River Systems Velocity is affected by the topography Gradient describes the steepness of the land’s slope Near the headwaters, the gradient is steep Near the mouth, the gradient is gentle

River Systems Stages of a River Youthful River Erodes stream bed more than the banks Steep V-shaped valleys Waterfalls and rapids are common Few tributaries

River Systems Mature River Many tributaries Erosion occurs along banks Wide, relatively flat valley Meanders- curves formed as erosion takes place Oxbow lakes can be formed as a meander straightens out

River Systems Old Rivers Low gradient Flows slower than a mature river Few, but rather large, tributaries Less erosion

River Systems Rejuvenated River An old or mature river whose gradient has become steeper due to movement of the Earth’s crust Step-like terraces are seen as the valley floor is uplifted and the river cuts through creating a new valley floor

Groundwater Precipitation that does not run off directly into streams will seep into the soil filling any air spaces between particles of rock and sediment. This water found beneath the Earth’s surface is called groundwater.

Groundwater A body of rock which stores water is called an aquifer. Regions with sediments such as sand and gravel, sedimentary rock, or fractured rock can all be areas with large aquifers.

Groundwater There are two main variables that help decide how much water can be stored by a particular type of rock. Porosity Permeability

Groundwater Porosity The percent of open spaces in the rock Sorting- well sorted particles of rock will be similar in size and results in high porosity. Poorly sorted rock will have low porosity Packing- Loosely packed particles will have plenty of pore space, tightly packed particles will have little or no pore space

Groundwater Permeability Permeability indicates how freely water passes through the open spaces in it Rock made of large, poorly sorted particles is the most permeable Large cracks will increase permeability Rocks that prevent the flow of water are said to be impermeable

Groundwater Zone of Saturation Water Table Layer of the ground where all of the pores are filled with water Water Table The upper surface of the zone of saturation. This level may rise or fall.

Groundwater Zone of Aeration Layer of ground between the water table and the earth’s surface. Upper portion near surface will be moist Lower portion near water table will be moist Middle region will normally be dry

Groundwater As water is removed from an aquifer, new water must take its place in order to recharge the aquifer This can be done either by rainfall or the movement of groundwater based on topography

Groundwater Ordinary Wells and Springs A well is a hole dug below the water table that fills with groundwater. A spring is a natural flow of groundwater to the earth’s surface that is found where a low spot in the ground is beneath the water table.

Groundwater Groundwater can be pumped out of a well faster than it flows through the ground. This lowering of the water table near the well is called a cone of depression.

Groundwater Artesian Wells and Springs Wells and /or springs whose aquifer is located beneath a layer of impermeable rock called a cap rock. Water is pushed to the surface by pressure so no pumping is required.

Groundwater If groundwater is located in a region where magma is close to the surface, hot springs can be formed. A hot spring must have water as warm as human body temperature (37˚C)

Groundwater Hot springs can mix with the soil to form mud pots, areas of hot, thick, bubbling clay. Hot springs that erupt above the surface are called geysers

Groundwater As groundwater passes through permeable rock it dissolves some of the minerals that make up the rock. Calcium, Magnesium, and Iron

Groundwater Hard water has large amounts of dissolved minerals Soft water has relatively few dissolved minerals Hard water can affect soap suds, taste, and leave deposits.

Groundwater Hardness

Groundwater In certain sedimentary rocks such as limestone, groundwater erosion can create caverns. As this water evaporates, the dissolved calcite solidifies forming stalactites and stalagmites

Groundwater Caverns close to the surface may be prone to having the roof collapse forming a sinkhole Sometimes a series of sinkholes occur that leave part of the roof of the cavern intact, this forms a natural bridge