Exam 1 Study Guide

What % of the human body is water?

65-70%

 What % of earth’s surface is water?

71%

 The majority of accessible freshwater _______.

is located in groundwater (about 29%)

In the US, groundwater accounts for _______.

40% of the water supply

In NC groundwater accounts for _______.

50% of the water supply

Rainfall mechanisms

1. orographic

2. frontal systems

3. convective

Orographic

Occurs when general circulation forces an air mass up and over a mountain range. The air mass reaches saturation vapor pressure, resulting in more precipitation on the windward side and rain shadow on the other side of the mountain. 

• a rainfall mechanism

Frontal Systems

two air masses of different temperature and moisture come together, and air is lifted at the frontal surface

• 1. warm front = warm air rides up and over a cold air mass- widespread, gentle rainfall

• 2. cold front = cold air mass replacing and lifting a warm air mass- high intensity, more localized, short duration rainfall

• a rainfall mechanism

Convective

Occurs due to excessive heating of earth’s surface that results in the layer of moist air adjacent to the surface to rise as an air mass. Condensation occurs, the latent heat of vaporization adds more energy, and more lifting occurs. This rapid uplift results in frozen water droplets, hail, and severe thunderstorms.

• a rainfall mechanism

Greenville NC receives approximately ______.

48 - 56 inches of rain per year

Meteorological drought

based on precipitation

Agricultural drought

based on soil moisture during the growing season (is the topsoil wet enough to grow crops?)

Controls on interception

 1. Growing vs dormant season - Growing season means more leaf area on trees/plants -> more interception

  2. Snow vs rain - typically more interception in rainstorms relative to snowstorms

  3. Stand density - more trees, more potential for interception

Potential evapotranspiration (PET)

 The maximum amount of water that could be lost from evaporation and plant transpiration. 

- assume an unlimited amount of water is present

Methods for estimating PET

1. Hamon method (requires air temperature data)

2. Penman method (requires radiation, vapor pressure, and wind speed data; → most physically based but requires expensive data)

Simple water budget Components

P = Q + ET

P = precipitation  

ET = evapotranspiration 

Q = runoff (River discharge)

Controls on infiltration

1. Soil water content - soils already saturated will be more likely to produce runoff → less infiltration

2. Soil porosity - soils with more connected void spaces can transmit water more readily than soils with less voids → more infiltration

3. Soil biological activity - worm holes, animal burrows, and etc. can increase porosity and infiltration

4. Soil litter layer - protects soil surface from crusting/compaction → increases infiltration

5. Soil frost → can reduce infiltration

Devices to measure infiltration rate

Double Ring Infiltrometer and the Constant Head Permeameter

Hydrograph

Graph of water levels over time

- can show how a river’s water level changes over a period of time in response to precipitation

Recharge

An increase in groundwater storage followed by a rise in water levels due to infiltration from precipitation.

- On the hydrograph, it’s observed as a gradual rise. After this period ends, there is a gradual decline in water levels.

What is one major difference in the water cycle of an urban area relative to a forest?

Urban settings have more impervious surfaces, like parking lots, rooftops, and roads. Due to these hard surfaces, there is less infiltration, leading to more runoff.

 Each soil is a mixture of _______.

sand, silt, and clay particles which help determine the soil texture

Adhesion

attraction of water and soil

- Positive side of water molecule (with hydrogens) attracted to negative surface charge of soil particles

Cohesion

attraction of water to water

- Negative side (with oxygen) of the water molecule is attracted to the positive side of another water molecule

Saturation

all pores are filled with water

Wilting point

water is still in the soil, but it is held too tightly to be absorbed by plants, causing them to wilt

Field capacity

water from macropores (large pores) has drained due to gravity

Soil water

water in the unsaturated zone, held to soil particles by surface tension and adhesion

Groundwater

water in the saturated zone (underground layer where all open spaces are filled with water)

Capillary fringe

zone just above the water table, where soil is almost completely saturated (99%), but is held in soil matrix and will not drain under gravity

Matric force

attraction of water to soil solids, responsible for adsorption and capillarity

Osmotic force

attraction of water to ions and other solutes (like salts)

Device that measures volumetric soil water content

Neutron scattering

Device that measures soil water potential

Tensiometer

Groundwater moves along a slope from ______.

high hydraulic head to low hydraulic head

Piezometer

Has a short screen that is below the water table → shows pressure across the screen (pressure head)

Wells

Has a longer screen that shows the water table surface → screen interval in saturated and unsaturated zones

- can measure hydraulic head

What is a method to determine groundwater flow direction?

3-point contouring method

- Graphical method that involves using the hydraulic head data from three observation wells.

- The depth to water for each well is subtracted from the elevation at the top of each well (this is the hydraulic head)

- The water elevation values are put into this formula: E_H - E_L/HL = E_H - E_I/x . The X value is the calculated distance from the well with the highest water elevation towards the well with the lowest water elevation (where the contour line will start).

- The flow direction is perpendicular to the contour line. 

Aquifer

Permeable rock or sediments that transmit water easily (ex. sand or gravel)

Aquifers in Eastern NC

• Yorktown aquifer

• Castle Hayne aquifer

• Beaufort aquifer

• Peedee aquifer

• Black creek aquifer

• Upper cape fear aquifer

• Lower cape fear aquifer 

What is the central coastal plain capacity use area (CCPCUA)?

A regulated portion of eastern NC where some aquifers have experienced dewatering, saltwater encroachment, and declining water levels that are not sustainable.

How are communities dealing with the CCPCUA rules?

- Utilizing more surface water supplies (Neuse Regional Water and Sewer Authority – Lenoir and Pitt counties from Neuse River; Martin county potentially using the Roanoke, Grenville Utilities using Tar River)

- Using injection wells to store treated surface waters in confined aquifers for later uptake → greenville utilities

- Utilizing other aquifer systems (Castle Hayne, surficial and Peedee aquifers – Jacksonville and Craven County)

- Agricultural users constructing surface water impoundments

- Purchasing water from other systems

- Industries investing in water reuse and conservation

Dewatering

Occurs when the water pressure drops below the confining unit, causing air to be introduced to the aquifer → results in the soil settling/collapse of the aquifer

Declining water levels

 Describes a decrease in surface elevation for bodies of water

Saltwater intrusion

Occurs in freshwater areas that experience a drop in water levels. This causes water to be drawn in from nearby saltwater sources, due to water naturally moving from areas of high to low pressure. 

Isotopes

A specific form of an element that have the same number of protons, but a different number of neutrons.

What can isotopes be used for?

In addition, with land-use information, isotopes can be used to find the source of pollution, especially nutrient pollution. This can be determined by the ratio of heavy to light isotopes.

pH

The negative log of the hydrogen ion (H+) concentration. It is used to indicate if a substance is acidic or basic.

- It can have a major impact on biological and chemical reactions

- There is an inverse proportion of H⁺ and OH^- ions, and the pH scale is logarithmic.

- pH of 6 has 10x more H+ ions in solution than pH 7, 100x more than pH 8, etc.,

pH of non-polluted streams

6-9

- varies due to the presence of organic acids or alkaline mineral deposits

Common types of microbial communities

Aerobes, anaerobes, and facultative

 Common fecal indicator bacteria used for water quality monitoring

Fecal coliform, enterococcus, and E. coli

DO (dissolved oxygen)

oxygen that has been incorporated into water

- required for the survival of many aquatic animals 

- standards: Trout waters > 6.0 mg/L; High-quality waters = 6.0 mg/L; most fish = 4 mg/L

- Impacted by water temperature (high temperature means low DO and vice versa) and organic matter (can deplete water of DO)

BOD (biochemical oxygen demand)

The amount of dissolved oxygen (DO) that aerobic microorganisms utilize to aerobically oxidize organic matter at 20 ^oC in 5 days 

- Most common parameter to determine strength of wastewaters in terms of biodegradable OM content

- Application: for design and evaluating efficiency of wastewater treatment plants

- An indirect measure of the organic content of a sample

- Sewage effluent typically has between 200-500 mg/L

Specific conductance

Measures electrical conductance due to dissolved substances in water per 1 cm path length at 25C 

- A measure of a substance’s ability to conduct electricity

Turbidity

Measure of the clarity of water 

- Influenced by the concentration of insoluble particles present and organic molecules

- Can be an indication of the presence of sediment, organics, and pollution

- Can be used to estimate suspended sediments

- High levels reduce the effectiveness of disinfection methods such as chlorination and UV (surface discharge systems)

Why are we concerned about nitrogen and phosphorus in water?

- Problematic nutrients in water in high levels

- Can cause eutrophication, leading to more aquatic vegetation and algal blooms

- Oxygen depletion

- Drinking water contamination

- Fish kills

- Algal blooms can also produce harmful toxins that can harm animals and public health.

- Cause odor problems

- Extra vegetation at the water surface that can inhibit the penetration of light into the water

Protozoan that if found in water supplies are potentially public health threats

 Giardia and Cryptosporidium parvum 

Autotrophic bacteria

Oxidize inorganic compounds as an energy source and use CO₂ for C source….. ex: cyanobacteria, Thiobacilli sp (deep sea vents, use sulfur)

Heterotrophic bacteria

Use organic matter as both carbon and energy source for synthesis

ex: denitrifying bacteria

Factors that influence the transmission of water borne diseases.

latency and infective dose

Groundwater discharge

Q = KA(dh/dl)

K is Hydraulic conductivity (from slug tests)

A is Area

dh/dl is Hydraulic gradient (from slope or 3-point contouring)

Water cycle

•Precipitation

•Interception

•Evapotranspiration

•Infiltration

•Groundwater

•Runoff

Textural Class triangle

All %’s must add to 100.

What is the difference in flow rate for pre and post development?

- During precipitation events in post development (urban settings), all runoff funnels at the same time to nearby water sources, causing large spikes in peak flow (flash flooding → higher peak flow) and then when there is no precipitation there will be low periods of flow rate

- In pre-development (natural settings), it takes a while for water in a water source to rise due to vegetation, infiltration, and movement through the groundwater system. There is more of a gradual rise in water levels/flow. When there is precipitation, it takes a while for the flow rate to drop because groundwater feeds the water source between rain events.

- Overall, natural areas have a higher base flow than urban areas, due to infiltration and a low number of impervious surfaces. 

Hydraulic gradient formula

The difference in hydraulic head between two points divided by the distance between them

(h₁ - h₂) / L