Water Resources and Hydrology Notes

The Water - Baseline Studies

Hydrology/Hydrogeology, Water Quality, and Ecology

• Key areas of study:

  • Hydrology/Hydrogeology

  • Water Quality

    • Freshwater Ecology

    • Oceanography

      • Marine Ecology

Hydrology: Changes and Impacts

• Change in Drainage Morphology: Alterations to streams and lakes.

• Change in stream, lake water depth

• Reduction in Stream Volumetric Flow: Decreased water flow in streams.

• Inducement of Flooding: Increased risk of floods.

• Water Resource Competition: Increased competition for water.

• Reduction/Depletion of Groundwater Flow: Diminished groundwater.

Watershed Characterization

• Essential for Environmental Impact Assessment (EIA).

• Provides baseline information.

Hydrological Attributes

• Components:

  • Physical Component

  • Hydrology

  • Water Quality

Measuring Hydrological Attributes

• Methods:

  • Field Measurements

  • Laboratory Analysis

  • Use of Secondary Data: From NIA, NPC, PNOC, water districts, watershed-related agencies, and local knowledge.

Channel Morphology

• Drainage net of the watershed.

• Description of hydrologic and sediment characteristics.

• Prediction of ungaged watersheds' performance, as seen on https://lotusarise.com/channel-morphology-upsc/

Channel Types

• Straight Channel

• Sinuous Channel

• Meandered Channel

• Braided Channel

• Anastomising Channel

Channel Morphology: Cross-section and Profile

• Measurement: aerial photos, maps, or field survey.

• Importance: determination of average slope and cross-section for natural flow computations.

Channel Morphology: Stream Ordering

• Methods: Horton’s and Strahler’s method.

• Bifurcation ratio: ratio of streams of any given order to the number of streams in the next lower order.

Channel Morphology: Stream Length and Slope

• Stream Length:

  • Measured using map measurers, compass, or dividers.

• Stream Slope:

  • Ratio between the difference in elevation and the stream length.

Channel Morphology: Stream-Length Gradient Index

• Formula:

  • SL = \frac{\Delta h}{\Delta l}
    Where:

  • \Delta h: Difference in elevation

  • \Delta l: Stream length

  • \text{O} = midpoint of reach

Channel Morphology: Drainage Patterns

• Types: dendritic, parallel, trellis, rectangular, radial, annular, and contorted.

• Rosgen classification: longitudinal, cross-sectional, and plane views of major level I stream types.

Drainage Patterns

• Dendritic

• Rectangular

• Radial

• Trellis

Channel Morphology: Stream Classification

• Based on pattern, regularity of flow, and size.

• Rosgen Classification: size based.

• Regularity of flow: perennial, intermittent, ephemeral.

• Stream ordering: classifying streams according to size.

Rosgen Classification of Natural Rivers

• Key characteristics include:

  • Entrenchment Ratio

  • Width / Depth Ratio

  • Sinuosity

• Stream Types:

  • A, G, F, B, E, C, D, DA

• Slope Range varying from > 0.04-0.10 to < 0.001

• Channel Material: BEDROCK, BOULDERS, COBBLE, GRAVEL, SAND, SILT/CLAY

• Values can vary by:

  • Entrenchment and Sinuosity ratios: +/- 0.2 units

  • Width / Depth ratios: +/- 2.0 units

Hydrological Attributes: Drainage Texture Parameters

• Describes runoff and infiltration behaviors of a watershed.

• Determined by the complexity, number, and length of the stream network.

Drainage Texture

• Drainage density:

  • Length of stream per unit area.

  • Measures efficiency of the stream in collecting and discharging water.

  • Inversely proportional to the size of individual drainage units.

• Stream frequency

• Drainage Intensity

Drainage Texture: Drainage Density Formula

• Formula:

  • Dd = \frac{L}{A}
    Where:

  • L = total length of all perennial and intermittent streams

  • A = area of the watershed

Drainage Texture: Stream Density Rules

• Mainstream counted as one.

• Tributaries of the next lower order are counted individually.

Drainage Texture: Stream Density Formula

• Formula:

  • Ds = \frac{N}{A}
    Where:

  • N = number of all perennial and intermittent streams

  • A = area of the watershed

Drainage Texture: Texture Ratio

• Ratio between the number of contour crenulations and the length of the perimeter.

• Contour crenulations indicate channels too small to be shown by stream symbols.

• Correlated with drainage density because the frequency of contour crenulations measures channel spacing.

Drainage Texture: Constance of Channel Maintenance

• Represents the area of watershed required to maintain one unit of drainage channel.

• Measure of the minimum limiting area needed for drainage channel development.

Drainage Texture: Length of Overland Flow (FL)

• Distance over which runoff will flow before concentrating into permanent channels.

Hydrological Attributes: Stream Flow Discharge

• Measurement: floating experiments, current meters, weirs (e.g., V-notch weir).

Streamflow Discharge: Floating Experiment Formula

• Formula:

  • Q = VA
    Where:

  • Q = Streamflow discharge (\text{m}^3/\text{sec})

  • V = streamflow velocity (\text{m}/\text{sec})

  • A = cross-sectional area of the stretch of stream (\text{m}^2)

Streamflow Discharge: Floating Experiment Steps

1. Set up the area by choosing a clear stretch and dividing it into three regions.

2. Obtain the depth, width, and length of each region.

3. Toss the floating object and record the time it reaches the endpoint multiple times.

Streamflow Discharge: Current Meter

• Measurements vary with stream depth.

  • Depth of 0.5 m: 2 measurements (20% and 80% of original depth, average obtained).

  • Less than 0.5 m: 1 measurement (60% of original depth).

• Pygmy current meter: used for shallow streams.

Streamflow Discharge: Hydrograph

• Plot of discharge and stage water level in stream versus time.

• Four parts: peak flow, rising limb, falling limb, and base flow.

• Stormflow hydrograph: graph of flow before, during, and after a specific storm event.

Hydrological Attributes: Sediment Load

• Sedimentation: transfer of soil particles by streamflow, becoming the sediment load.

• Two types: suspended load and bed load.

• Challenge: obtaining a representative sample for suspended load determination.

Hydrological Attributes: Sediment Load Determination

• Methods for bed load determination: volumetric surveys or setting up traps behind catchment basins and measuring the weight per unit volume of the materials trapped.

Hydrological Attributes: Hydrology Definition

• Science dealing with the occurrence of water on earth.

• Includes physical/chemical properties, transformations, combinations, and movements.

• Focuses on water's course from precipitation to discharge into the sea or return to the atmosphere.

Hydrological Attributes: Hydrological Cycle

• Processes: precipitation, interception, infiltration, evaporation, transpiration, evapotranspiration.

Hydrological Attributes: Precipitation

• Descending of condensed water vapor in the form of precipitate.

• Forms: rain, snow, dew, fog, and hail.

• Sources: frontal storm, convective, orographic, tropical activity.

Hydrological Attributes: Precipitation and Return Period

• Floods are a result of precipitation.

• Return period formula:

  • Tr = \frac{1}{P}

  • Where:

    • Tr = Return period

    • P = Probability to occur each year

Hydrology: Interception

• Process: precipitation is caught and held by vegetation.

• Interception loss: part of the precipitation on the canopy that doesn’t reach the ground because it evaporates or is absorbed by plants.

Hydrology: Interception Effects

• Reduces water available to the basin hydrologic cycle.

• Reduces transpiration of vegetation.

• Washes solid particles and dissolves carbon from leaves, affecting water chemistry.

Hydrology: Factors Affecting Interception

• Vegetation characteristics: growth form, plant density, plant community structure.

• Meteorological characteristics: precipitation intensity, duration, wind speed, type, frequency.

Hydrology: Infiltration

• Passage of water through the soil surface into the soil horizon.

• Infiltrated water percolates or moves downward within the soil.

• Infiltration capacity: maximum rate at which a soil can absorb water.

Hydrology: Factors Affecting Infiltration

• Soil characteristics (porosity, texture, structure, and moisture).

• Precipitation (type, duration, intensity).

• Land cover (affects runoff flow rate).

• Slope of the land.

• Evapotranspiration (affects soil moisture content).

Hydrology: Significance of Infiltration

• Recharges groundwater for continuous water supply.

• Determines surface runoff (overland flow) production.

• Two conditions of overland flow: Horton’s and Saturation overland flow.

Hydrology: Evaporation

• Change in state of liquid water into vapor, transferring the vapor to the atmosphere.

• Latent heat of vaporization: energy required to evaporate a gram of water (600 cal/g).

Hydrology: Transpiration

• Transfer of water in vapor form through plant stomates.

• Stomates open to exchange gas and prevent overheating.

• Prevents desiccation.

Hydrology: Evapotranspiration (ET)

• Sum of evaporation and transpiration.

• Potential evapotranspiration (PET): maximum rate of ET that could occur.

• Actual evapotranspiration (AET): real rate of ET that does occur.

Hydrology: Evapotranspiration Factors

• PET is determined by climatic variables: temperature, solar radiation, humidity, and wind.

• AET depends on vegetation, stage of growth, soil moisture, and climatic variables.

• Other factors: vegetation, land use, latitudinal/elevational position, weather condition.

Evapotranspiration: AET Estimation

• Methods: adjustment of pan evaporation measurement, soil microcosm-lysimeter, gas flux, and watershed studies.

• Pan estimates: AET measured through pan evaporation measurement. Pan coefficient (0.6-0.9) used to determine AET.

Evapotranspiration: AET Estimation Formula (Pan Estimates)

• Formula:

  • AET = Cp * Etpan

  • Where:

    • Cp = Pan coefficient (0.6-0.9)

    • ETpan = Pan evaporation measurement

Evapotranspiration: AET Estimation (Weighing Lysimeters)

• Mass of soil supporting plant growth is placed in a container on a large scale.

• Water enters through precipitation and leaves as outflow or evapotranspiration.

• Uses the water budget concept.

Evapotranspiration: AET Estimation (Water Budget Formula)

• Formula:

  • ET = (P - R) +/- (\frac{\Delta s}{\Delta t})

  • Where:

    • P = Precipitation

    • R = Run-off

    • \Delta s = change in weight

    • \Delta t = change in time

Evapotranspiration: AET Estimation (Gas Flux Measurement)

• Expensive and difficult method.

• Plastic tent constructed over vegetation, and air is blown through the tent.

• ET is estimated by measuring humidity and flow rate of incoming and outgoing air.

Evapotranspiration: AET Estimation (Watershed Studies)

• Common method of estimating ET.

• Uses water balance equation: P = Q + ET + S

  • Where:

    • P = precipitation

    • Q = stream flow

    • ET = evapotranspiration

    • S = change in soil/bedrock storage

Evapotranspiration: ET Determination Using Watershed Studies

• Formula, derived from the water balance equation:

  • ET = P - (R + I)

  • Where:

    • P = Precipitation

    • R = Run-off

    • I = Interception

Evapotranspiration: General Equation

• Equation:

  • T = KcKsPET

  • Where:

    • Kc = crop factor (ranges from 0.1-1.2, depending on the vegetation stage of growth)

    • Ks = soil factor = \frac{F}{S}, where F = \theta v - WP, and S = FC - WP

    • PET = potential ET

Evapotranspiration: PET Estimation

• Methods: hydrometeorological equations, energy balance, and Eddy covariance.

• Hydrometeorological equations: use temperature, wind speed, relative humidity, and solar radiation values (e.g., Penman’s equation and Penman-Monteith equation).

Evapotranspiration: PET Estimation (Energy Balance)

• Equation: \lambda E = Rn + G - H

  • Where:

    • \lambda E = energy required to change liquid to gas

    • Rn = net radiation

    • G = the soil heat flux

    • H = the sensible heat flux

Evapotranspiration: PET Estimation (Eddy Covariance)

• Fast fluctuations of vertical wind speed correlated with fast fluctuations in atmospheric water vapor density.

Hydrological Attributes: Water Quality

• State of the biological, chemical, physical properties of water (potable, contaminated, etc.).

• Contaminant: undesirable substance not normally present or unusually high concentration of a naturally occurring substance; becomes a hazard when present in elevated concentrations.

Hydrological Attributes: Water Quality - Pollutants

• At elevated concentrations, pollutants produce pollution. Two types of sources: point (exact location) and non-point.

• Different water contaminants: Nitrate, Viruses, organics, phosphate, bacteria, pharmaceuticals, and inorganic materials.

Water Quality: Sampling and Measurement

1. Collect samples downstream the project site extending to the next source of contaminants.

2. Establish sampling stations 1 km apart following the river’s course from the project site.

3. Collect samples at the middle part of the river 1 m above the ground and another a meter below the surface.

4. Place water samples for chemical and biological parameters in a sterile container.

5. Preserve other samples through refrigeration and transport all samples to the laboratory for analysis.

Water Quality: Sampling and Measurement Considerations

• Type of constituents being sampled dictates the sample size to be used.

  • e.g., Phosphate - 100ml, Salinity - 250 ml

• Stream water quality attributes:

  • Physical (color, odor, temperature, conductivity, etc.)

  • Biological (pathogens, microorganisms)

  • Chemical (DO, BOD, pH)

Water Sampling Notes

• Avoid trapping air.

• Label properly:

  • Sample Name

  • Sampling Station/Site

  • Date of Collection

  • Time of Collection

• Store in 1-40°C for further processing & analyses.

On Site Measurements

• Turbidity (Nephelometric Turbidity Units)

• Secchi Disk

• Hand-Held Meter Probes:

  • Can measure electrical conductivity, pH, temperature, Dissolved Oxygen, salinity & turbidity

• Meter Stick:

  • water depth

• Floater & transect line:

  • flow rate

Parameters Measured in Laboratory

• Water samples should be stored in 1-4°C for transport in the lab

  1. Microbial analysis & bacteria

  2. Total suspended solids

  3. Total N & P

  4. BOD

  5. PAH

  6. Surfactants

  7. Metals: Cr (VII), total Hg, etc.

  8. Total Petroleum Hydrocarbons

  9. Pesticides & herbicides

  10. Br, Cl, F, I, SO4, B, S, etc.

Groundwater Quality

• Groundwater contains various chemical constituents at different concentrations.

• Most soluble constituents in groundwater come from soluble minerals in soils and sedimentary rocks.

• A smaller part originates in the atmosphere and surface water bodies.

Water Usage and Classification

• The quality of Philippine waters should be maintained safely and satisfactorily according to their best usages.

Water Body Classification and Usage of Freshwater

• CLASS AA: Public Water Supply Class I - For uninhabited watersheds requiring only disinfection.

• CLASS A: Public Water Supply Class II - Sources requiring conventional treatment.

• CLASS B: Recreational Water Class I - For primary contact recreation.

• CLASS C:

  1. Fishery Water for propagation and growth of fish.

  2. Recreational Water Class II - For boating, fishing, etc.

  3. For agriculture, irrigation, and livestock watering.

• CLASS D: Navigable waters.

Water Body Classification and Usage of Marine Waters

• CLASS SA:

  1. Protected Waters - national/local marine parks, reserves, sanctuaries.

  2. Fishery Water Class I - Suitable for shellfish harvesting for direct human consumption.

• CLASS SB:

  1. Fishery Water Class II - Suitable for commercial propagation of shellfish.

  2. Tourist Zones - For ecotourism and recreational activities.

  3. Recreational Water Class I - For primary contact recreation.

• CLASS SC:

  1. Fishery Water Class III - For the propagation and growth of fish and other aquatic resources

  2. Recreational Water Class II - For boating, fishing or similar activities

  3. Marshy and/or mangrove areas declared as fish and wildlife sanctuaries

• CLASS SD: Navigable waters

Water Quality Criteria for Conventional & Other Pollutants Contributing to Aesthetics & Oxygen Demand for Fresh Waters

• Parameters include Color, Temperature, pH, Dissolved Oxygen, BOD, Total Suspended Solids, Total Dissolved Solids, Surfactants, Oil/Grease, Nitrate, Phosphate, Phenolic Substances, Total Coliforms, Chloride as Cl, Copper

Water Quality Criteria for Toxic & Other Deleterious Substances for Fresh Waters (For the Public Health)

• Parameters include Arsenic, Cadium, Chromium (hexavalent), Cyanide, Lead, Total Mercury, Organophosphate, Aldrin, DDT, Dieldrin, Heptachlor, Lindane, Toxaphane, Methoxychlor, Chlordane, Endrin, PCB

Water Quality for Conventional & Other Pollutants Affecting & Exerting Oxygen Demand for Coastal and Marine Waters

• Parameters: Arsenic, Cadium, Chromium (hexavalent), Cyanide, Lead, Total Mercury, Organophosphate, Aldrin, DDT, Dieldrin, Heptachlor, Lindane, Toxaphane, Methoxychlor, Chlordane, Endrin, PCB

Significant Parameters for Selected Types of Industries

• Examples:

  • BEVERAGE INDUSTRY: BOD5, Ph, Suspended Solids, Settleable Solids, Oil and Grease

  • CEMENT, CONCRETE, LIME & GYPSUM PH, Suspended Solids, Dissolved Solids, Temperature

  • DAIRY PRODUCT PROCESSING: BOD5, COD, Ph, Suspended Solids, Dissolved Solids, Settleable Solids

Approved Methods of Analysis

• Examples:

  • Arsenic: Silver Diethyldithiocarbamate Method (Colorimetric)

  • BOD5: Azide Midification (Dilution Technique)

  • Boron: Carmine Method (Colorimetric Method)

  • Cadmium: Atomic Absorption Spectrophotometry, (wet ashing with concentration HNO3 + HCl)