ABE 66 PPT 2

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Questions and Answers

What is the primary focus of sustainable water resources management?

Prioritizing household water consumption

Maximizing industrial water usage

Exclusively focusing on environmental preservation

Meeting current needs without impacting future generations (correct)

What percentage of available fresh water is classified as groundwater?

75%

50%

97% (correct)

30%

Which principle does not belong to the principles of sustainability?

Profit Maximization (correct)

Efficiency

Equity

Environmental Protection

What impacts the yield potential of a well?

Geological characteristics of the aquifer Signup and view all the answers

Which type of water source is generally more consistent than surface water?

Groundwater Signup and view all the answers

Which of the following is a common quality problem with groundwater?

Extreme hardness Signup and view all the answers

What can cause groundwater levels to drop significantly?

Drought periods Signup and view all the answers

What characteristic of aquifers helps manage precipitation variability?

Thickness of water-bearing strata Signup and view all the answers

What is the consequence if the drawdown in a confined aquifer is so significant that the cone of depression penetrates the top of the aquifer?

The aquifer begins to dewater. Signup and view all the answers

During a pump test, what is the maximum recommended duration to evaluate the capacity of a well for extended use?

30 days Signup and view all the answers

Which factor is NOT assumed in the equations for analyzing well hydraulics?

Steady-state conditions exist in nature. Signup and view all the answers

What is a critical evaluation point for the yield calculation in an unconfined aquifer system?

Drawdown approaches the thickness of the aquifer. Signup and view all the answers

What impact does a well being screened only in part of the aquifer have on flow analysis?

It requires a more complex analysis. Signup and view all the answers

Which measurement is essential for estimating the hydraulic conductivity of an unconfined aquifer?

Depth to static water table. Signup and view all the answers

What is the hydraulic conductivity value provided in the sample problem for the confined aquifer?

$2 × 10^{-5}$ m/s Signup and view all the answers

Which factor is least likely to affect the performance of a well in a confined aquifer?

Weather patterns. Signup and view all the answers

What is true about the water table?

It is the level at which underground water pressure equals atmospheric pressure. Signup and view all the answers

Which type of formation is classified as an aquitard?

Formation that can store water but transmits it slowly. Signup and view all the answers

Which describes a confined aquifer?

It has an aquitard above it restricting water movement. Signup and view all the answers

Primary porosity is defined as:

The void space between particles. Signup and view all the answers

What characterizes an aquifuge?

It cannot store or transmit groundwater. Signup and view all the answers

Secondary porosity refers to:

Voids created from the dissolution of larger structures. Signup and view all the answers

Which of the following is true about unconfined aquifers?

They receive water freely from the land surface. Signup and view all the answers

What is the primary function of an aquifer?

To store and transmit groundwater. Signup and view all the answers

What term describes the zone not completely saturated with water?

Unsaturated zone Signup and view all the answers

Which zone is located below the saturated zone and experiences plastic deformation under pressure?

Zone of rock flowage Signup and view all the answers

What defines the water table?

The upper surface of the saturated zone Signup and view all the answers

What is the capillary fringe?

A zone just above the water table with virtually saturated porous media Signup and view all the answers

What causes perched waters to form?

Localized saturation above a less permeable layer Signup and view all the answers

Which of the following zones would you expect to find all pore spaces filled with water?

Saturated zone Signup and view all the answers

Which statement about the water table is true?

It is the upper surface of the saturated zone Signup and view all the answers

In what circumstance is water in the capillary fringe evaluated during urban planning?

Drainage system design Signup and view all the answers

What defines a good aquifer based on hydraulic conductivity?

Greater than or equal to $10^{-5}$ m/s Signup and view all the answers

Which variable is not included in the formula for steady-state well discharge in an unconfined aquifer?

Thickness of the confined aquifer ($d$) Signup and view all the answers

In the context of well hydraulics, what does the term 'cone of depression' refer to?

The phenomenon when pumping exceeds recharge rate Signup and view all the answers

What is the primary purpose of the Siechardt formula?

To determine the radius of influence around a well Signup and view all the answers

What does the variable $d$ represent in the discharge formula for a confined aquifer?

Thickness of the confined aquifer Signup and view all the answers

Which of the following conditions indicates an aquifer with insufficient water resources?

Less than $10^{-9}$ m/s Signup and view all the answers

What is represented by $q$ in the discharge equations for aquifers?

Discharge rate Signup and view all the answers

Which factor does NOT affect the radius of influence according to the Siechardt formula?

Time since pumping started Signup and view all the answers

In the formula for well discharge of confined aquifers, which of the following terms represents the height of the potentiometric surface?

$h_2$ Signup and view all the answers

What does high permeability in an aquifer typically indicate?

Good water storage capability Signup and view all the answers

Study Notes

Groundwater Zones and Terminologies

Unsaturated zone (vadose zone): Void spaces in soil and rock aren't completely filled with water.
Saturated zone: Voids are completely filled with water; located below the vadose zone.
Zone of rock fracture: Combination of unsaturated and saturated zones where rock fractures due to crustal stress.
Zone of rock flowage: Below the saturated zone; rock deforms plastically under pressure; water is inaccessible.
Water table (phreatic surface): Upper surface of the saturated zone; water level in a well.
Capillary fringe: Zone above the water table where porous media is nearly saturated; water isn't easily extractable.
Perched water: Localized saturated zone above a less permeable layer (e.g., clay).

Sustainable Water Resources Management

Aims to meet current water needs without compromising future needs.
Balances demands of agriculture, industry, domestic use, and environmental conservation.
Key principles: Equity, Efficiency, Environmental Protection.

Water Sources

Groundwater: About 97% of available freshwater; less seasonal than surface water; levels fluctuate.
Surface water
Rainwater

Groundwater Characteristics

Found almost everywhere; highly variable in access, quantity, and quality.
Well yield depends on aquifer porosity, hydraulic conductivity, fracturing, and thickness.
Potential quality issues: extreme hardness, dissolved salts, iron.

Porous Media Types

Primary porosity: Void space between particles.
Secondary porosity: Voids larger than primary particles. Examples include well-sorted sand, poorly sorted sand, sand with precipitates, fractured rock, and rock with dissolution channels.

Aquifer Classifications

Aquifer: Stores and transmits groundwater in sufficient quantities; saturated stratum of high permeability.
Aquifuge: Cannot store or transmit groundwater.
Aquitard: Stores but transmits groundwater slowly; relatively impermeable layer restricting vertical flow.
Aquiclude: Contains groundwater but doesn't transmit it sufficiently; more restrictive than an aquitard. An aquifer is not an underground lake or river.

Aquifer Types and Hydraulic Conductivity

Unconfined aquifer: No aquitard above; water percolates freely from the surface.
Confined aquifer: Aquitard forms the upper boundary.
Hydraulic conductivity classifications: ≥ 10⁻⁵ m/s (good aquifer), 10⁻⁹ – 10⁻⁵ m/s (poor aquifer), < 10⁻⁹ m/s (insufficient water). Good aquifers have high permeability and porosity.

Well Hydraulics: Steady-State Discharge

Unconfined aquifer: Equation provided for discharge (q) calculation using hydraulic conductivity (k), radial distances (r₁ and r₂), and water level heights (h₁ and h₂).
Confined aquifer: Equation provided for discharge (q) calculation using hydraulic conductivity (k), aquifer thickness (d), radial distances (r₁ and r₂), and potentiometric surface heights (h₁ and h₂).

Well Hydraulics: Radius of Influence

Siechardt formula: Empirical formula (provided) to estimate radius of influence (R) using drawdown (SW) and hydraulic conductivity (k).

Cone of Depression

Occurs when pumping rate exceeds groundwater recharge.

Sample Problems

Provided examples calculating discharge from a confined aquifer and hydraulic conductivity of an unconfined aquifer, using the previously stated equations.

Critical Evaluation of Results

Drawdown approaching aquifer thickness in unconfined systems may invalidate yield calculations.
Excessive drawdown in confined aquifers can lead to dewatering and more complex flow analysis.
Steady-state conditions are rarely found in nature; long-term tests are recommended.
Equations assume wells fully penetrate aquifers.

Assignment

Enumerate and discuss major large-scale dams in the Philippines, including location, construction dates, storage capacity, purpose, manufacturer, watershed area, services, and other relevant details.

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Description

This quiz covers essential concepts related to groundwater zones and terminologies, including unsaturated and saturated zones, the water table, and perched water. It also delves into sustainable water resources management principles that aim to balance human needs with environmental conservation. Test your knowledge on these critical topics in water science and management!