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
Set up the area by choosing a clear stretch and dividing it into three regions.
Obtain the depth, width, and length of each region.
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
Collect samples downstream the project site extending to the next source of contaminants.
Establish sampling stations 1 km apart following the river’s course from the project site.
Collect samples at the middle part of the river 1 m above the ground and another a meter below the surface.
Place water samples for chemical and biological parameters in a sterile container.
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
Microbial analysis & bacteria
Total suspended solids
Total N & P
BOD
PAH
Surfactants
Metals: Cr (VII), total Hg, etc.
Total Petroleum Hydrocarbons
Pesticides & herbicides
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:
Fishery Water for propagation and growth of fish.
Recreational Water Class II - For boating, fishing, etc.
For agriculture, irrigation, and livestock watering.
CLASS D: Navigable waters.
Water Body Classification and Usage of Marine Waters
CLASS SA:
Protected Waters - national/local marine parks, reserves, sanctuaries.
Fishery Water Class I - Suitable for shellfish harvesting for direct human consumption.
CLASS SB:
Fishery Water Class II - Suitable for commercial propagation of shellfish.
Tourist Zones - For ecotourism and recreational activities.
Recreational Water Class I - For primary contact recreation.
CLASS SC:
Fishery Water Class III - For the propagation and growth of fish and other aquatic resources
Recreational Water Class II - For boating, fishing or similar activities
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)