cive230 lec 9 - water resources and water scarcity issues

how many people lack access to improved water supply, or a source of water protected from sewage contamination

900 million

how much sewage and other effluents drain into the world’s waters every day

2 million tons

what are the major repositories of water on earth (in order from most to least)

ocean seawater, geologic (groundwater, soils, etc.), atmosphere, living organisms

residence time

the length of time a chemical substance (chemical element or compound) remains in a defined reservoir/repository

residence time equation

t=M/F, where M is mass in reservoir and F is mass flow rate

biogeochemical cycles

Biogeochemical cycles refer to how chemical elements (carbon, oxygen, hydrogen, nitrogen, phosphorus) that are prerequisites for life, flow from one reservoir to another reservoir.

Hydrologic cycle/water cycle

describes the movement of water from one reservoir to another

evaporation

the process of converting liquid water from surface water sources to gaseous water that resides in the atmosphere

transpiration

when water is conveyed from living plant tissue, especially leaves, to the atmosphere

evapotranspiration

evaporation + transpiration

condensation

through this process water converts from gas phase to liquid water by cooling the water molecules

precipitation

water moves from the atmosphere to the surface of the earth

infiltration

through this process precipitation seeps into the ground

runoff

through this process water flows over saturated land or impervious surface

what percentage of all water is freshwater

2.5%

total volume of freshwater

35.2 km³

distribution of freshwater

68.9% ice caps and glaciers, 29.9% groundwater, 0.80% permafrost, 0.40% surface and atmosphere

what is the largest source of water for human consumption

groundwater

groundwater

the water found underground in the cracks and spaces in soil and sand. It is also found in aquifers (large water body) between rocks or earth layers

water budget

Water budget refers to the balancing of the flows of water into and out of a watershed or system

watershed

a land area that topographically collects rainwater and drains to a particular point - also called natural drainage basin/catchment area that collects and discharges surface water through one outlet

sustainable water use

• Current consumption/use does not degrade the quality for future generations;

• Current consumption/use does not degrade the quality for downstream activities such that the costs required to restore the original quality is prohibitive or infeasible.

types of water uses

withdrawal use, nonwithdrawal use, consumptive use

withdrawal use

refers to the use of water for any purpose which requires that water be physically removed from the source.

nonwithdrawal use

The use of water for any purpose which does not require that it be removed from the original source. Example: Navigation

consumptive water use

water removed from available supplies without return to a water resources system (e.g., water used in manufacturing, agriculture, and food preparation that is not returned to a stream, river, or water treatment plant)

virtual water

water required for the production of commodities (m3 water/kg commodity) - hidden volume of water used in the production and supply chain of goods and services, rather than the water directly consumed by individuals (“virtual” because it’s not physically present in the product)

green virtual water

the portion of precipitation that is absorbed by soil and used by plants for growth through transpiration

blue virtual water

refers to surface and groundwater sources, like rivers, lakes, and aquifers, that are used in production processes

grey virtual water

water that has been polluted by human activities, such as industrial processes or agricultural runoff, and requires dilution to meet water quality standards

water footprint

Water Use + Net Virtual Water Imports

• establishes the linkage between water

  consumption in one place and water use and the associated environmental impacts in another place

economic water scarcity

when a region or population lacks the financial resources or infrastructure to access existing water supplies, even if those supplies are physically available - most prevalent in Africa

is groundwater abstraction and recharge sustainable in north america?

not sustainable (esp in USA) because of the high abstraction rates but generally low recharge rates - groundwater table is declining in many parts of NA