The Hydrologic Cycle

Salt water vs. fresh water In this class, we will be mostly Concerned with fresh water (terrestrial).

Less than 1% of the Earth’s freshwater is on the surface at any time. groundwater. 20% of the freshwater flows through the ground – groundwater.

Basic Cycle Ocean Evaporation Evaporation (ET) runoff Precipitation Aquifer Infiltration Evaporation Precipitation Evaporation/ET Surface Water Groundwater

Water Residence Times Get this image from the mac to place here

Stream channel Stream : body of running water that is confined to a channel and moves downhill due to gravity

Drainage Basin Drainage Basin: total area drained by a stream. Larger streams have larger drainage basins. The size and composition of the sediment carried by the stream depends on the nature of the drainage basin.

Dissolved Load Suspended Load Bed Load

Braided Channel Meandering Channel Straight Channel

Fig Braided Streams Streams with high sediment loads deposit lots of channel bars. The stream moves around the bars, finding its way through the barriers. Usually found near sediment source areas and/or areas with easily eroded substrate.

Braided Stream

Fig Meandering Stream Deposition point bars Deposition occurs on point bars, where stream velocity is low Erosion cutbanks Erosion occurs on cutbanks, where stream velocity is high

Fig Meandering Stream Deposition point bars Deposition occurs on point bars, where stream velocity is low Erosion cutbanks Erosion occurs on cutbanks, where stream velocity is high

Figure 14.14

Fig Meandering Streams oxbow lake

Fig Flood Plain: Flood Plain: area habitually flooded by a stream at high water. Contains fine-grain sediment deposited during flooding Natural levee: Natural levee: low ridges formed along sides of main stream channel during flooding.

Fig Flood Plain: Flood Plain: area habitually flooded by a stream at high water. Contains fine-grain sediment deposited during flooding Natural levee: Natural levee: low ridges formed along sides of main stream channel during flooding.

Water In (Inflow) Surface runoff Groundwater influx Discharge from upstream Direct precipitation Water Out (Outflow) Capacity (shape-dependent) Rate (slope-dependent) 93 m 150 m I O normally I > O channel fills If channel fills completely, river can overflow banks and flood Stream Budget

Flooding

Flooding at River Park, Rock Hill September, 2004 Flooding along the Catawba river was caused by extreme rainfall resulting from an unusual series of powerful hurricanes and tropical storms.

Precipitation – the basic water resource GW Adapted from: GWP (M. Falkenmark), 2003, Water Management and Ecosystems: Living with Change Blue & Green Water - perspective

Why so much for agriculture? Most countries want/need to feed themselves. No water = no plants = no food

Photosynthesis 6CO 2 + 6H 2 O C 6 H 12 O 6 + O 2 C3 plants – 1 gram biomass per grams water transpired C4 plants – 1 gram biomass per grams water transpired CAM plants – 1 gram biomass per grams water transpired

Water use and farms Average water needed per acre of crop –Soybean (C3 plant) = 737,100 liters H 2 O –Corn (C4 plant) = 862,500 liters H 2 O Considering that many farms are hundreds to thousands of acres…that’s a lot of water!! ---Note that corn is a more massive crop. ---Also note that CAM plants are primarily habit the desert and are not irrigated.

Typical Domestic Water Use 10 – 40 L/person/day (water scarce) 50 – 100 L/person/day (low-income) 100 – 600 L/person/day (high-income) –Differences in domestic freshwater use: Piped or carried Number/type of appliances and sanitation

Water Stress Index Based on human consumption and linked to population growth Domestic requirement: – m 3 /person/year (water scarce) – m 3 /person/year (high-income) Associated agricultural, industrial & energy need: –20 x domestic requirement –73 – 292 m 3 /person/year –730 – 4380 m 3 /person/year Total need: –77 – 307 m 3 /person/year (water scarce) –767 – 4599 m 3 /person/year (high-income)

Water Stress per International River Basin

Colorado River Basin Colorado River water usage –Water “rights” from river (in million acre feet) Colorado 3.85 New Mexico0.84 California 4.4 Arizona2.8 Nevada0.3 Utah1.7 Mexico1.5 Total Average River Flow = 15.5

Population growth in Colorado River Basin