Water Resources Management in Disaster Areas: 2008 EES Summer School

Posted on Jan 14, 2025 in Biochemistry

EES Summer School: Ecological Management of Disaster Areas 2008

Water Resources Management

Questions:

1. What is the Hydrological Cycle and How Can Water Balance Be Quantified?

Caused by solar energy.

C: ocean → evaporation → precipitation → runoff (→ evaporation) → infiltration (→ ocean) → subsurface runoff → ocean

Annual Water Balance in the World:

Quantification: Precipitation (P) = Evapotranspiration (E) + Runoff (R)

520 (km³) = 484 + 36

Some Points:

• Water moves from one reservoir to another (from river to ocean, from ocean to atmosphere).
• Water moves around the cycle by physical processes of evaporation/evapotranspiration, condensation, atmospheric precipitation (solid – as snow or hail, liquid – rain), surface runoff, infiltration, subsurface runoff, subsurface flow.

Applying in Catchment: (Surface water flows through one outlet, determined by water divide)

Water balance: Precipitation equation:

Precipitation = Runoff + Actual Evaporation ± ΔW (changes in the storage)

ΔW = Δ soil + Δ groundwater storage → storage in saturated and unsaturated zones

2. What are Both Catchment and Management Characteristics that Significantly Affect Surface Runoff?

Catchment: Surface water flows through one outlet. It is determined by a water divide.

• Rainfall must be managed through a network of channels into storages (like catchments).
• Architectural structures: Often ignored (closed river channels in towns, leading water underground).

Catchment Characteristics:

a) Physio-geographical:

• Climatic: Precipitation, temperature, air-humidity, air-pressure (saturation deficit), wind-speed and direction.
• Soils: Dispersity-granulometry, soil categories, soil types, permeability, hydrolimits, etc.
• Geology: Rocks-igneous, metamorphic, sedimentary, permeability.
• Geomorphology: Sediment transport regime – E, T, S.
• Vegetation Cover: Forest, grassland, etc.
• Retention and Accumulation of Catchment: → Retention: Canopy, litter, soil (short-term) and Accumulation: Lakes, reservoirs (long-term).
• Man–made Impacts: Land use, exhalations, etc.

b) Physio-geometrical:

• Catchment Area:    A [km²]
• Catchment Width:       B = [km] → L … length of main river
• Catchment Slope:  J_s = → H_max = catchment highest peak, H_min = catchment outlet
• River Slope:  J_r  = [-] →  H_r … river spring altitude        
• Density of River Network:   D = → The highest D, the most intensive hydrological cycle.
• Percentage of Forestation: [%]
• Management of the Catchment:          Land use, road system, cascade of storage (reservoirs), polders, dikes.

3. What are the Major Reasons for Floods?

Main Reasons:

1. Rainfall (water depth or quantity water in mm)
2. Rain intensity (i) (i= depth / time = m / hour)

Other Important Reasons:

• Too much water (at the same place in a short time) – huge intensity, depth.
• Unregulated runoff – no infiltration.
• Huge areas without vegetation etc…
• Hydrometeorological situation: Small catchments: Torrential rainfalls; Big catchments: Combinations of regional and torrential rainfalls, most important criteria: Depth P (mm) and intensity I (mm .min^-1) of rainfall.
• Antecedent saturation of the catchment active zone: Antecedent precipitation index; and soil moisture deficit (SMD).
• Measures for increasing retention / accumulation of water (decreasing direct (surface) runoff).

4. How to Mitigate Harmful Flood Impacts?

Through runoff transformation, it mitigates flood waves through cascade storage or dikes, ditches, terraces in order to interrupt runoffs.

Also:

• Good agricultural practices                – forestry         – land use        – road network (drainage)
• Landscape structure, mosaic displacement   – natural retention, wetlands
• Natural hydrographical network: Geomorphologic diversity, conveyance of discharges, channel vs. inundation
• Erosion control measures: Depressions, dikes, terraces, torrent control, gully control
• Mini-races, bifurcations, blind streams, deltaic areas, natural depressions/ inundations
• Small reservoirs, (fish) ponds, retention barriers      – dykes and polders
• Weirs and dams

5. Write the Water Balance Equation

Precipitation equation:

Precipitation = Runoff + Actual Evaporation ± ΔW

ΔW = Δ soil + Δ groundwater storage → changes in water storage (saturated and unsaturated zones)

6. Define Rainfall Depth and Intensity

• Rainfall Depth: Amount of rain (1 mm) = 1 m²× 10^{-3 m = 10-3 m3}= 1 l (how many liters in 1 mm of rainfall on  1 m² of surface)
• – Rainfall Intensity (R) = /t (mm/s) = amount of rain over a particular time i =
• Height of rain, time of duration

7. What are the Basic Principles for Climate Change Scenarios?

Kurzets’s Curve (4 baseline scenarios):

• A1: Global economy (rapid economic growth – open markets, technological development)
• A2: Continental markets (heterogeneous world – divided regions, security)
• B1: Global cooperation (service & info-based economy; global security, government intervention)
• B2: Regional communities (regional identity, behavioral change, export subsidies abolished)

8. What are the Major Flood and Water Erosion Control Measures?

• Organizational Erosion Control: Land management and road network, permanent grassing and afforestation, crop displacement and belt growing crops.
• Agronomic Erosion Control Measures: Contour plowing, mulching.
• Technical Erosion Control Measures: Terraces, dry gully control, torrent control, protection of high slopes (with bioengineering), ex.: Ditches next to roads, leading rain-water away by system of channels.

9. Can You Express the Relation Between Hydrological Probability and Return Period?

P=1/N → P [%] = Hydrological Probability that the same rain can come again

P= P x 100

P – Periodicity, means that rain can repeat X times during X years (tells us in how many years can the same rain repeat e.g. once in 200 years – a 200 year rain). P must be obtained from graph (head of water vs. time) – according to rain intensity

A Return Period (N) =  is an estimate of the interval of time between events (earthquake, flood or river discharge flow of a certain intensity or size)

=  statistical measurement denoting the average recurrence interval over an extended period of time

=  usually required for risk and also to dimension structures so that they are capable of withstanding an event of a certain return period (with its associated intensity).

10. Why Water Scarcity Becomes a More Actual Global Problem? Give the Major Reasons

• Externalities (flood, drought),
• Improper use of water “water abuse” (irrigation, sanitary),
• Climate (lack of water).

Causes of Water Scarcity:

• Population growth     
• Food production       
• Climatic change and variability        
• Land use
• Water quality            
• Water demand                      
• Sectoral resources and institutional capacity
• Poverty and economic policy                                   
• Legislation and water resource management
• International waters  
• Sectoral professional capacity          
• Political realities        
• Sociological issues

11. What Forces Affect the Shape of Rivers in a Landscape (River Meandering)?

River Channel Formation:

 Internal Geological Forces: Volcanic + Seismic → formation of primary earth relief

External Forces: Ice movement + flowing water → formation of secondary relief:

Catchment formation: – gravity (general force) +  centrifugal force

The River Meandering is due to:

• Transversal water flowing – spiral flowing
• Heterogenic displacement of roughness along wetted perimeter
• Earth rotation (Coriolis effect)

12. How to Reduce Surface Runoff on a Catchment?

Mitigation of adverse impacts of runoff can take several forms:

 a) Land use development controls aimed at minimizing impervious surfaces in urban areas

 b) Erosion controls for farms and construction sites

 c) Flood control programs

 d) Chemical use and handling controls in agriculture, landscape maintenance, industrial use, etc.

This is achieved by altering the topography of land, erecting barriers to the flow of water and by

increasing the opportunity for infiltration. The practices followed include:

• Land grading and leveling;
• Bunding, terracing, basin listing, criss-cross ridging;
• Retaining crop residues after harvest;
• Reducing depth as well as frequency of irrigation.

Also with biotechnical measures (ditches, dams …etc.)

13. How to Increase River Capacity?

When channel slope, roughness and cross-section profiles are smaller?

•  Considering river channel together with inundation(s) (flood plain) as one „water body“ (diking, poldering) in open landscape environment. Connect the channel.
•  Necessity to dredging bottom in narrow profiles? (What about benthos?)
•  Individual specific way urbanized areas (bypasses, deeper bottom, hydraulic structures, fish passes, etc.).

14. What are the Major Outlines for a River Restoration (Revitalization)?

Outlines:

• Good quality of water: Central water purification (self-purification, inside purification). There are 3 steps of purification: a) Physical purification (filtration), b) Biological purification (bacteria-microbes) and, c) Chemical purification (chlorine, ozonification).
• Biological property: Good environment for flora and fauna. And the contact with terrestrial and aquatic zones.
• Diversity (biodiversity, morphological diversity).
• The riparian vegetation, banks…
• Water capacity (urbanized vs. open landscapes).

River Restoration – The Outlines

• Water Quality Standard: Land use and management on the catchment; Efficiency of water purification plants, purity of water; Self-purification process.
• Biological Regime: Species/tropical structure; migration of biota  (fish traveling up stream);  interconnection of zones;  riparian vegetation.
• Diversifications:  In a route (meandering);  in a longitudinal profile (pools and rapids);  in a cross-section profile (non-symmetrical in a curve).
• Discharge Capacity:  Re-evaluation of criteria;  change of land use along a river route;  local obstacles;  polders and dikes.
• Movable Bottom: Bed load movement; Bottom morphology (ripples); Bottom zoology (benthos: invertebrates).

15. What are the Principles of Different Concept of Biotechnical Improvements on Small Rivers in Open Landscape (Extravilan) and in Urbanized Areas (Intravilan)?

Open Areas: Almost no damage, if the water happens to spill from banks during floods.

Urban Areas: Problem with floods – different approach needed, because the river flows through urbanized area which we must protect.

16. Define the Main Reasons for Reservoirs. What is the Difference Between Dam and Dike?

Main Reasons:

• Water accumulation and  retention
• Fish breeding
• Recreation and/or environmental purpose and special purposes (irrigation, re-pumping, etc.)

Dike–  is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels. To prevent floods: An embankment built along the shore of a sea or lake or beside a river to hold back the water and prevent flooding.

Dam – is a barrier that impounds water or underground streams – controlling flow of water: A barrier of concrete or earth that is built across a river or stream to obstruct or control the flow of water, especially in order to create a reservoir.

17. Write the List of the Significant Hydrological Processes

Precipitation (P): Condensation of water-vapor (dew-point). Atmospheric precipitation: Liquid (rainfall, dew), Solid (snow, hoarfrost, hail, frost).

Evaporation (E): Free-water evaporation, bare soil evaporation, transpiration, evapotranspiration, potential evapotranspiration, evapotranspiration of snow and ice.

Subsurface Runoff: Subsurface water (soil water, absorptive, capillary; groundwater, gravity water).

Surface Runoff

Infiltration

Interception/Percolation

18. What is the Shear Stress (Equation)?

τ₀= R*y*J (Pa)

J=Slope

y= p.g (y= specific gravity, p=density(kg/m³)and g= acceleration gravity) mil*10=10⁴ n.m^-3              

R= Hydraulic radius (m)

Function of material (density), magnitude of grain.

• Is defined as the component of stress coplanar with a material cross section.
• Shear stress arises from the force vector component parallel to the cross section.

19. What is the Chezy Equation and How Does it Express?

• Estimate the flow capacity of the filled up water orchard inside ditch.
• To approximate the water flow in the filled up water orchard inside ditch use equation 1 and 2.

(1)Chezy equation.V = C√R.J  (m/s)                                       R – hydraulic radius of the ditch

(2) Continuity equation.Qd = S .V                                           Qd – water flow of inside ditch

                                                                                         C – Manning´s coefficient of velocity

20. What is the Rating Curve (Q – Curve)?

Is a graph of discharge versus stage for a given point on a stream, usually at gauging stations, where the stream discharge is measured across the stream channel with a flow meter.

• Is usually plotted as stage on X-axis versus discharge on Y-axis of the profile: Y = f (Q)

21. Fundamentals in Groundwater Flow (Darcy Law)

• Glacial sediments
• Fluvioglacial sediments
• Fluvial sediments
• Cracks, karstic, etc..

Velocity = Hydraulic Conductivity * Slope of Ground Water

22. Basics of Irrigation (Purpose and Technology)

Source of artificial application of water to the land or soil.

•  It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall.
• As a few other uses in crop production, which include protecting plants against frost, suppressing weed growing in grain fields and helping in preventing soil consolidation.
• Irrigation systems are also used for dust suppression, disposal of sewage, and in mining.
• In surface irrigation systems, water moves over and across the land by simple gravity flow in order to wet it and to infiltrate into the soil.
• Irrigation is often studied together with drainage.
• The different types of irrigation systems are flood, row or furrow, aerial, and drip and sprinkler.

Purposes of Irrigation:

• Providing insurance against short duration droughts.
• Reducing the hazard of frost (increase the temperature of the plant).
• Reducing the temperature during hot spells.
• Washing or diluting salts in the soil softening tillage pans and clods.
• Delaying bud formation by evaporative cooling.
• Promoting the function of some micro organisms.

Irrigation basis on water balance equation:

W= Precipitation +Subsurface Inflow + Surface Flow – Evapotranspiration – Runoff – Subsurface Outflow →

Result is negative then we need irrigation. If the result is positive we may need drainage.

23. Basics of Drainage (Purpose and Technology)

Drainage is the natural or artificial removal of surface and sub–surface water from a given area.

• Many agricultural soils need drainage to improve production or to manage water supplies.
• The main purpose of drainage is to provide a favorable root environment, which is conducive to the proper growth of plants.

Functions:

• To prevent or reduce waterlogging (accumulation of water in root zone) and water ponding (accumulation of excess water on soil surface).
• To control salinity.
• To reclaim land.
• To sustain land.

Drainage System: Controls water table (in summer works as a reservoir of water when weather is too dry) and removes excess rainfall water (in winter).

Most Commonly Used Drainage System: Consists of drains, primary drains and secondary drains; the primary drain collect all the water, leads it towards the outlet.

Infiltration Ditch

• Not underground.
• Contains different mixtures of soil to allow infiltration.
• Location depends on infiltration rate of soil.
• Depth and width should correlate with rainfall intensity.
• Does not lead the water away but helps it soak into the surrounding soil.

24. Water Problems of Wastes, Landfill Technology

Centralized Collection Systems:

Historical development and new materials 

Problems with Inappropriate Wastewater Treatment:

• Organic pollution of surface water (depletion of dissolved oxygen which is dangerous for aquatic organisms, especially for fish).
• Eutrophication by nitrogen and phosphorus compounds with all consequences like deterioration of water quality for recreational purposes or use for drinking water preparation.
• Health risk (bacterial contamination of surfaced water; the effect of endocrine disruptors on human health).

25. What is Saturated Hydraulic Conductivity?

Hydraulic Conductivity: A property of that describes the ease with which water can move through pores or fractures. Depends on the intrinsic permeability of the material and on degree of saturation.

K is a parameter that shows how fast the water can flow in saturated porous environment.

K …filtration coefficient (saturated hydraulic conductivity).

Characteristic K values (in mm .s^-1)

Clay ……10^-5 – 10^-4

Loam …..10^-4 – 10^-3

Sand ……10^-3 – 10^-1

26. Infiltration Ditch and Open Drain Ditch as a Protection Against Erosion Processes and Surface Runoff

Infiltration ditch has no slope, open drain ditch has a slope and the water flows out the ditch.

• Infiltration ditch: Prevents water from infiltrating.
• Draining ditch: Drains water out.

27. Describe an Infiltration Process

Infiltration process → movement from soil surface – through active and soil zone of soil water zone, then by infiltration of water by gravity forces to transitional zone – then to upward capillary flux zone by capillary forces (capillary water forms) then infiltration to groundwater.

Water always moves from saturated zones to unsaturated; mostly – infiltration from soil surface to soil subsurface.

28. What are the Basic Requirements on Rivers?

29. River Erosion (Scouring) and Sedimentation (Deposition). Do You Know the Criteria of River Erosion?

Movement = Erosion → no sedimentation, no erosion

Chezy Equation for River Erosion

V>V_kr → Erosion and we need some structures to prevent this erosion.

Formation of sediments (from catchments and channels)= process of water erosion

Categories and Properties of Sediments

• Suspended load: To 7mm (overlapping v 0,1 – 7,0 mm – according to shear stress = t₀)
• Bed load: Sand: 0,1 – 7,0 mm
• Gravel: 7,0 –  70,0 mm
• Stones: 70,0 – 500,0 mm
• Boulders: Over 500 mm

30. Restoration Principles and Riparian Vegetation

Riparian Vegetation  

♦Requirements:

• Stand (topographical, climatological, soil)
• Protection (bank protection)
• Ecological (abundance, diversity, environment)
• Harvest (to minimize)

♦Accompanying Riparian Vegetation:

Beyond bank line, main purpose: Landscape architecture, changing groups, convex banks, dominants, view through (vista).

♦Protective Requirements:

• Dense net of roots
• Flexible willow sprouts-dumping water velocity
• Herbal growth (canopy) – similarly
• Bank-line stabilization
• Biocorridor belt – zoocenologic viewpoint
• Improvement of self-cleaning effect of river 
• Oxygen enrichment
•  Aesthetic function
•  Timber production