Water Supply and Management

Discussion Objectives Important Properties of Water Distribution of Water The Water Cycle Major Uses of Water Human Impacts on the Water Cycle

Properties of Water Hydrogen bonding:

Properties of Water Hydrogen bonding leads to the important characteristic of high specific heat. Takes a lot of energy to melt or vaporize water; Implications: Does not change temperature rapidly; Influences climates; Organisms can regulate temperature.

Climate Effects Near Large Bodies of Water

Properties of Water Water is the “universal solvent”: Dissolves some materials rapidly (salts) and some materials very slowly (granite). Major transport mechanism in plants and animals: nutrients and pollutants. Major transport mechanism of Non-Point Source Pollutants locally and regionally.

Properties of Water

Properties of Water Water has a high surface tension: Implications: Facilitates movement through membranes and vascular tissues; Water surface is a habitat to organisms.

Properties of Water The solid form of water is less dense that it liquid form. Implications: Global temperature; Ice floats…important characteristic for fish?

Properties of Water Water is transparent, therefore light can penetrate the surface and allow photosynthesis to occur. Implications: Oligotrophic systems vs. Eutrophic systems

Groundwater and Streams Water found below the Earth’s surface, within the zone of saturation, below the water table Water table, recharge zones, discharge zones, aquifer, cone of depression Effluent Stream A type of stream where flow is maintained during the dry season by groundwater seepage into the channel Influent Stream A type of stream that is everywhere above the groundwater table and flows in direct response to precipitation

How Much Water is There? Approximately 97% of the Earth’s water is in the oceans. About 2% is in the polar ice caps (freshwater). The remaining 1% is freshwater found in rivers, streams, lakes, groundwater and atmospheric water vapor.

Global Water Supply

Global Distribution of Water Is the global distribution of water uniform?

Water Usage Do All Nations Use Water the Same? Developed nations that have high industrial and/or agricultural output consume large quantities of water. Global per capita water usage is approaching 200 gallons/day.

Major Water Use Categories Off-stream use: Uses that temporarily or permanently remove water from its source (e.g., irrigation or cooling waters). If not returned, it called “consumptive use”. In-stream use: Uses that do not remove water from its source (e.g., hydroelectric power or recreation). Multiple uses can cause conflict between users.

In Stream Water Use

Water Use Trends In The U.S. Water for irrigation and and the thermoelectric industry have been the largest water users since the 1950s. Water usage for domestic consumption has increased with the population increase, but industrial consumption has decreased.

Water Use Trends in The U.S. From 1950-1975, water use steadily increased with the population increase. From 1975 to the present, water use has remained constant although the population has grown. This trend suggests that water conservation and management techniques have been mildly successful.

Water Budget for the U.S.

Factors Influencing Water Distribution Global Air Flow Patterns:

Factors Influencing Water Distribution Local Air Flow Patterns:

Factors Influencing Water Distribution Evaporation Precipitation Run-off Infiltration Percolation

Evaporation Approximately 66% of total precipitation is lost through evaporation or evapotranspiration processes. Evaporation and transpiration rates vary depending on season, vegetation, soils, land use and local climatic conditions.

Precipitation Precipitation rates are a function of relative humidity. Approximately 34% of the total precipitation enters groundwater or surface water supplies. Is this enough to compensate for current water usage patterns?

Precipitation as a function of relative humidity:

Mean Annual Precipitation

Water Run-Off Water stays on the land surface. Influenced by local topography.

Percolation

Sources of Our Water Supply Drinking water supplies come from surface water bodies and groundwater aquifers. Approximately 51% of the U.S. population gets drinking water from underground wells. A higher percentage in Southeast Missouri gets its water from private wells. Are these private wells required to be tested to determine if the water is free of biological or chemical contamination?

What is an Aquifer? Aquifer: Underground soil or rock formations that contain pore space or fractures that may become filled with water. Aquifers near the ground surface are called surficial or unconfined aquifers (any potential problems with this type?). Aquifers separated from surficial aquifers by an impermeable layer are called confined aquifers.

Aquifer Recharge and Discharge Aquifers can be recharged by surface infiltration and by streams. This is a long-term process…takes years to replace lost water. Groundwater moves very slowly. Aquifers can recharge surface water bodies.

Groundwater Overdraft The total groundwater supply in the U.S. is large, however, it is unevenly distributed and withdrawals exceed recharge in some areas (e.g., Ogallala Aquifer). The excessive removal of groundwater is called “overdraft”.

Human Impacts on the Water Cycle Physical Impacts: Deforestation; Dams/Flow Diversion/Channelization; Creating Impervious Surfaces.

Impacts of Deforestation

Damming of Rivers

Effects of Stream Channelization Stream channelization is the widening, deepening, clearing or lining of existing streams. Positive effects: Improve drainage; Flood control; Erosion control; Improve navigation.

Effects of Stream Channelization Environmental effects: Alteration of stream habitat; Alteration or removal of streamside vegetation and habitat; Removal of water storage capacity in wetlands; Removal of wetlands; Loss of aesthetic quality of the stream.

Impervious Surfaces Increased runoff. Source of pollutants. Reduction in groundwater recharge. Ex. 5 cm rain ¼ acre wood: 6 mm runoff ¼ acre housing project: 18 mm runoff

Overdrawing of Water Supplies Overdrawing from surface sources causes a drop in water levels that may affect habitat and organisms occupying the reservoir or lake. Groundwater: Lowering of the water table; Land subsidence; Saltwater intrusion.

Overdrawing of Groundwater

Overdrawing of Groundwater

Land Subsidence

Land Subsidence

Saltwater Intrusion

Saltwater Intrusion

Sustainable Water Use Sustainable water use: The use of water resources by people that allows society to develop and grow into an indefinite future without causing the degradation of the components of the water cycle or the ecological systems that depend on it.

Sustainable Water Use Planning Sustainable use criteria: Sufficient water volume to maintain human health; Sufficient water volume to maintain ecosystems; Maintaining water quality standards; Providing for the renewal of water resources; Promoting water-efficient technology and practice; Appropriate pricing of water resources.