1. Vignesh Sridharan & Eunice Ramos KTH
Hydrology and Water systems planning and management using modelling techniques
Vignesh Sridharan & Eunice Ramos
KTH
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste.

2. What is hydrology ? Simple definition-the science of water
Technical definition-occurrence, distribution and circulation of water
Water exists in different physical forms (vapor, liquid, solid etc.)
Circulation of water in the Hydrosphere-Hydrological Cycle
Closed Loop system involving different process which transform water into different phases.
Hydrology and water systems modelling form one of the core components of the CLEWs framework.
For a layman, what is hydrology is, it is simply the science of water;
however, the technical definition is the occurrence, distribution and circulation of water.
When we talk of the occurrence distribution and circulation of water, it may be either in the gasses phase or in the water vapor form or in the liquid phase. And when we talk of its circulation, it is in the hydrosphere.
Hydrosphere, discontinuous layer of water at or near Earth’s surface. It includes all liquid and frozen surface waters, groundwater held in soil and rock, and atmospheric water vapour.
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

3. Hydrological Cycle
We look at this hydrologic cycle, let us say starting from ocean, due to the heat energy that is provided by the sun, the water starts evaporating from oceans in the form of clouds. Then condenses to liquid state to form clouds and due to the wind action, it moves over the land masses. And then onto the land, it will precipitate in the form of precipitation
and this precipitation can be in any form, there are various forms of precipitation (rain, hail, snow and many other different forms).
Part of this precipitation is converted into vapor through evapotranspiration and part of it will become what is called run off.
What happens to this runoff? This run off finally, goes into the ocean through streams and rivers. And part of this precipitation, which falls on the earth, becomes infiltration. Infiltration is the part of the water or precipitation that goes into the ground, as we know, and this then percolates deep and goes into a ground water. This ground water also, after a very long time, in the form of base flow, goes back to oceans through the rivers and streams.
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

4. Hydrological Cycle
We look at this hydrologic cycle, let us say starting from ocean, due to the heat energy that is provided by the sun, the water starts evaporating from oceans in the form of clouds. Then condenses to liquid state to form clouds and due to the wind action, it moves over the land masses. And then onto the land, it will precipitate in the form of precipitation
and this precipitation can be in any form, there are various forms of precipitation (rain, hail, snow and many other different forms).
Part of this precipitation is converted into vapor through evapotranspiration and part of it will become what is called run off.
What happens to this runoff? This run off finally, goes into the ocean through streams and rivers. And part of this precipitation, which falls on the earth, becomes infiltration. Infiltration is the part of the water or precipitation that goes into the ground, as we know, and this then percolates deep and goes into a ground water. This ground water also, after a very long time, in the form of base flow, goes back to oceans through the rivers and streams.
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

5. Where is the water globally ?
Total: ⁶ km³
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

6. Who is consuming water ?
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

7. Why do we need to study water resources?
There is an increasing need to answer questions
How much water will be available in the rivers in a specific time
How much water can be pumped out of the ground
Will I have enough water for the hydro power plants
Will the precipitation be enough to get a good agricultural produce
If not where will the water come from to irrigate the crops
Will there be enough water for the industrial sector
………..
In order to answer many such questions, a good understanding of the hydrological cycle and accurate estimation of potential demand is necessary
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

8. Water resources modelling-why do it?
The need to carefully estimate the supply and demand side in the hydrological cycle requires good understanding of
The physical phenomenon
Mathematical representation of the same
A model is a representation of reality in simple form based on hypotheses and equations
Developing a model is an art which requires knowledge of the system being modeled, the user’s objectives, goals and information needs, and some analytical and programming skills.
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

9. Water resources modelling-How to do it?
Perceptual Model “Think Like a Watershed”
Understanding of the Earth System
Not constrained by mathematics
Conceptual Model
Synthesis (simplification) of the perceptual model
Requires specifying
System boundaries
Relevant inputs, state variables and outputs
Physical laws to be obeyed and simplifying assumptions
Different conceptual models = different hypotheses of system behavior
Numerical Model
Spatial discretization and temporal integration of the governing model equations
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

10. Water resources modelling-How to do it?
What is a water shed?
A watershed is the area of land where all of the water that falls in it and drains off of it goes to a common outlet. Watershed boundaries are defined by the shape of the land (topography). This means that watersheds are like bathtubs. Imagine that the bathtub is the watershed, and the drain is the river. Any water that falls inside the tub (watershed) will eventually go down the drain (river) carrying dirt and soap with it. The high sides of the tub (like mountains and hills) keep the water from ending up on the floor (or in other watersheds).
The watershed is the basic unit used in most hydrologic calculations relating to water balance or computation of rainfall-runoff. The watershed boundary (Divide) defines a contiguous area, such that the net rainfall or runoff over that area will contribute to the outlet. The rainfall that falls outside the watershed boundary will not contribute to runoff at the outlet.
Input: Rain, Snow, Hail etc..
Output: Discharge
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

11. Water resources modelling-How to do it?
Perceptual Model “Think Like a Watershed”
Understanding of the Earth System
Not constrained by mathematics
Conceptual Model
Synthesis (simplification) of the perceptual model
Requires specifying
System boundaries
Relevant inputs, state variables and outputs
Physical laws to be obeyed and simplifying assumptions
Different conceptual models = different hypotheses of system behavior
Numerical Model
Spatial discretization and temporal integration of the governing model equations
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

12. Water resources modelling-How to do it?
Land component of the water cycle (Clark et al., 2008)
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

13. Water resources modelling-How to do it?
Perceptual Model “Think Like a Watershed”
Understanding of the Earth System
Not constrained by mathematics
Conceptual Model
Synthesis (simplification) of the perceptual model
Requires specifying
System boundaries
Relevant inputs, state variables and outputs
Physical laws to be obeyed and simplifying assumptions
Different conceptual models = different hypotheses of system behavior
Numerical Model
Spatial discretization and temporal integration of the governing model equations
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

14. Water resources modelling-How to do it?
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

15. Water resources modelling-How to do it?
A watershed is the area of land where all of the water that falls in it and drains off of it goes to a common outlet. Watershed boundaries are defined by the shape of the land (topography). This means that watersheds are like bathtubs. Imagine that the bathtub is the watershed, and the drain is the river. Any water that falls inside the tub (watershed) will eventually go down the drain (river) carrying dirt and soap with it. The high sides of the tub (like mountains and hills) keep the water from ending up on the floor (or in other watersheds).
The watershed is the basic unit used in most hydrologic calculations relating to water balance or computation of rainfall-runoff. The watershed boundary (Divide) defines a contiguous area, such that the net rainfall or runoff over that area will contribute to the outlet. The rainfall that falls outside the watershed boundary will not contribute to runoff at the outlet.
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

16. Steps in Watershed modelling
Objective
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

17. Steps in Watershed modelling
Model Selection
Selection of model based on study objectives, watershed characteristics and availability of data
Time scale, hydrologic detail
Computation speed available
Input data
Topologic information
Digital elevation model (DEM)
Flow direction maps derived from DEMs
Drainage/watershed areas
River Networks
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

18. Steps in Watershed modelling
DEM: Digital file that stores the elevation of the land surface in a specified grid cell size (e.g., 30 meters)
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

19. Steps in Watershed modelling
Input data
Hydrological Information
Flow depth,
Streamflow discharge
Peak discharge
Daily flow volume
Annual flow volume
Base flow & Interflow
Stream-aquifer interaction
Water table and ground water info
Annual Groundwater recharge
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

20. Steps in Watershed modelling
Input data
Meteorological Data
Temperature
Precipitation
Wind Speed
Humidity
Snow & Glacial info
Solar Radiation
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

21. Steps in Watershed modelling
Input data
Geographic Data
Land Use
Land Cover
Natural resources map (oil, gas, Uranium etc.)
Administrative Boundaries
Transboundary resource maps
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

22. Steps in Watershed modelling
Input data
Pedologic Data (soil characteristics)
Soil type, texture, and structure
Soil condition
Soil particle size, diameter, porosity
Soil moisture content and capillary pressure
Steady-state infiltration,
Saturated hydraulic conductivity
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

23. Steps in Watershed modelling
Evaluation and refinement of Objectives
Evaluate and refine study objectives in terms of simulations to be performed under different watershed conditions and data availability
Calibration & Verification of the model
Model calibration involves selecting a measured set of input data (rainfall, channel routing, land use and so on) and measured output hydrographs for model application
Calibrate model using historical rainfall, streamflow and existing watershed conditions.
Verify model using other events under different conditions while maintaining same calibration parameters.
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

24. Steps in Watershed modelling
Model calibration
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

25. Steps in Watershed modelling
Simulation and Sensitivity analysis using the model
Perform model simulations using historical or design rainfall, various conditions of land use and various control schemes for reservoirs, channels or diversions.
Perform sensitivity analysis on input rainfall, temperature, and other hydraulic parameters as required.
Precipitation
Soil parameters
Hydraulic conductivity
Soil water holding capacity
Evapotranspiration
Flow routing parameters (for event-based modelling)
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

26. WEAP-The Water Evaluation and Planning System
Generic, object-oriented, programmable, integrated water resources management modeling platform
Try WEAP in one hour
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

27. WEAP-The Water Evaluation and Planning System
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH

28. Total Availability: 100 Units
Water balances A
City A
Water Demand : 40 Units
Total Availability: 100 Units 60 40
How the planning model works – some supply with a demand.
The next few slides show how water is distributed and tracked in the WEAP21 model.
Legend:
Red Circle = Demand Site
Blue Line = River (arrow points downstream- value at the top in blue represents the headflow of the river)
Green Line = Transmission Link (brings water from supply to demand)
Black Line = Represents where the water is flowing and how much
This slide – 100 units of water coming in via headflow of the river, 40 units are pulled from the river to meet the demand, leaving 60 units to continue downstream
15/11/2018

29. Water balances A City A Water Demand : 40 Units
Total Availability: 100 Units
Transmission capacity: 30 units
Unmet demand : ? 30
Here there is an infrastructure constraint on the transmission link (maximum allowed is 30 units)
100 units of water supplied via the head flow of the river
While the demand site is asking for 40 units, it will only receive 30 units because of the constraint on the transmission link.
This leaves 70 units to continue downstream
15/11/2018

30. Water balances A City A Water Demand : 40 Units
Total Availability: 100 Units
Transmission capacity: 30 units
Downstream water Requirement: 80 Units
Unmet demand : ? 70
IFR Met
Here there is a minimum flow requirement downstream of 80 units of water.
There is no constraint on the transmission link, but the flow requirement has a higher priority than the demand site.
100 units supplied as headflow, 1 priority is downstream flow requirement of 80 units, which leaves only 20 units for the demand site. The demand site is unmet by 20 units.
15/11/2018

31. Water balances City A Water Demand : 40 Units
City B Water Demand : 60 Units
Total Availability: 100 Units
Priority City A : 1
Priority City B : 2
Unmet demand at A : ?
Unmet demand at B : ?
This example shows the priority system in WEAP21.
Each demand site is given a priority (represented in the schematic by the black number in the red circle). Higher priorities receive water before lower priorities. The water will be distributed equally among demand sites of the same priority.
In the schematic the small holder demand has the higher priority. Since there is only 100 units of water supplied, the large farmer’s demand is unmet by 10 units.
If the large farmer had a higher priority then the small holder would only receive 30 units (a 10 unit deficit).
15/11/2018

32. Water balances City A Water Demand : 40 Units
City B Water Demand : 60 Units
Total Availability: 130 Units
Priority City A : 1
Priority City B : 2
Unmet demand : ?
The orange line represents a 20 unit return flow from the 40 unit demand site.
Here we have flow requirements on each river that have the highest priority. The 40 unit demand has a higher priority than the 70 unit demand. The 40 unit demand prefers water from river 1 (30 unit headflow) over water from river 2 (100 unit headflow).
The 40 unit demand site receives 10 units from river 1 (20 units on river 1 goes to the flow requirement). The 40 unit demand site also receives 30 units from river 2. River 2’s flow requirement will be met by the 20 unit return flow. Therefore, the 70 unit demand site will receive all 70 units from river 2.
15/11/2018

33. Thank You
11/15/2018
Summer School on Modelling Tools for Sustainable Development June 2017, ICTP, Trieste. Organizers: UNDESA, UNDP, ICTP, Cambridge University, KTH