THE HYDROLOGIC CYCLE
The Hydrologic Cycle
The Hydrologic Cycle - Fresh Water Storage Reservoir % of Total Fresh Water Glaciers (Frozen)76% Groundwater22% Rivers & Lakes < 2% Although it only makes up < 2% of total fresh water on earth, surface water is the most utilized and perhaps precious natural resource!
The Hydrologic Cycle How Does Water Move Within The Cycle?
The Hydrologic Cycle 1) RIVER SYSTEMS A)Important source of fresh water. B)Most important agent of erosion. C)Most abundant continental landform. D)Essential to agriculture & industry
Three Main Parts To A River System Collection system; Transportation system; Dispersing system
DIFFERENCES IN RIVER SUB-SYSTEM CHARACTERISTICS
The Collection System – A Drainage Basin
Types of Drainage Basins – Controlled by Geology
The Dynamics of Stream Flow 1)Velocity 2)Discharge 3)Channel Parameters 1)Roughness 2)Dimensions 4)Sediment Load 5)Gradient and Base Level The Transportation System
1) VELOCITY – Straight Channel
1) VELOCITY – Curving Channel
High V: Erosion LowV: Deposition 2) GRADIENT
MEASURING DISCHARGE (Q): Q m 3 /sec = V (AVG. ) X Width meters X Depth meters
4) SEDIMENT LOAD AND TRANSPORTATION
TRANSPORTING SEDIMENT
Ideal Stream Profile Increasing discharge, velocity & sediment load Decreasing gradient, turbulence & competence Base level – level of deepest possible erosion.
Dynamic Equilibrium – “You can never change just one thing about a stream.” The sensitive, ever-evolving balance between erosion and deposition. Graded Stream: erosion = deposition. If deposition > erosion, stream builds up its bed, thus increasing gradient and average velocity to restore balance. If erosion > deposition, stream erodes bed, decreasing gradient and velocity.
Departures from Equilibrium Waterfalls – signs of a shifting balance: increased discharge or gradient
Dam That Stream! A System Out of Balance Dam Effects Upstream deposition Discharge of clear, turbulent water & potential erosion. Elimination of floods (reduced competence); Choke off down- stream sediment flow. Disturbed ecosystems
Meandering Streams
Floodplains have a purpose!