Water System - Lecture

Water Cycle

  • Precipitation: rain and snow

  • Evaporation: water —> vapor

  • Transpiration: plants release water

  • Condensation: vapor —> water: clouds

  • Runoff: water flows overland

  • Infiltration: water into soil

  • Percolation: flow of water from soil —> aquifer

Sources and Sinks of Water

  • Source: pool that releases more water than it accepts

    • Ex: oceans, rivers, lakes, soil, glaciers, groundwater

  • Sink: accepts more water than it releases

    • Ex: oceans, rivers, lakes, soil, glaciers, groundwater

  • Whether a water pool is considered a source of sink is dependent on precipitation, eruption, and extraction/withdrawal rates

Types of Water

  • Fresh vs saline vs mixed

    • 2.5% vs 97.5% vs minimal

    • salt water is 3.5% saline

  • A. Fresh water: lakes, reservoirs, rivers, wetlands, snow pack, glaciers (majority), atmosphere, groundwater, watershed

  • 1. Surface water: located atop Earth’s surface

    • watersheds: drainage basins, area of land drained by a river

    • floodplains: areas near rivers that flood

      • surface water becomes groundwater via infiltration

      • floodplains are good areas for agriculture

  • 2. Groundwater: water located beneath Earth’s surface hold in pores of soil or by rock

    • aquifers: porous formations of rock, sand, or gravel that hold water

      • confined (between 2 layers) and unconfined (permeable)

  • B. Saline: salt water

    • Oceans

      • salt in ocean comes from rocks on land via runoff and rivers

        • rainwater contains dissolved CO2 and chemically weathers and erodes rocks on land

          • composition of ocean water: sodium chloride (NaCl)

          • 3.5% weight of seawater is dissolved salts

Types of River Channels

  • 1. Braided: complex network of channels chocked out by sediment

  • 2. Meandering: moves in sweeping bends

    • cutbank: erosion

    • pointhars: deposits

  • 3. Bedrock: straight channels (rare)

Wetlands

  • Soil is saturated with shallow standing water with vegetation

    • extremely valuable

    • ex: marshes, swamps, bogs

  • Function: slow runoff, reduces flooding, filters pollutants

  • Problems:

    • people have drained wetlands for agriculture

      • wetlands are affected by withdrawing water, building dums and levees and introducing pollution

Water Supply, Use, and Management

  • Water supply on surface depends on rates of precipitation, evaporation, stream flow, and subsurface flow

    • humans and climate drive water supply

  • Water budget: inputs, outputs, and storage of water in a system

  • Groundwater supply, nearly half of US population uses groundwater as primary source of drinking water

    • due to the cost of pumping and exploration, much less than the total quantity of groundwater

In Class:

  • Desalinization: complex and expensive process to remove water from salt

  • Distilled water: pure H20, evaporating then condensation water