A consulting company is assessing the impact of a proposed new dam on streamflow

Question

A consulting company is assessing the impact of a proposed new dam on streamflow within the downstream catchment. The consultants have historical data for rainfall, evapotranspiration and streamflow. They have developed a hydrological model of the catchment and have used Monte Carlo simulation to estimate future streamflow. Some results of the Monte Carlo simulation are shown in the figure below. Based on these results, the consultants claim the risk of extinction to sensitive species in the riverine ecosystems is 'low' to 'moderate'. They say that allocating some water to environmental flows will ameliorate this risk. Average Monthly Streamflow (m3/s) 70000 60000 50000 40000 30000 20000 Zum 10000 Jan Feb Mar Apr May before dam construction Jun Jul Aug Sep Oct Nov Dec after dam construction (model estimate) (a) Do you think the consultants' conclusions are reasonable? Why or why not? (three marks) (b) When modelling using Monte Carlo simulation, what are the four key types of uncertainty that need to be considered? Briefly describe each one. (four marks) (c) Write two questions, specifically relating to this dam modelling example, asking the consultants to explain how they accounted for uncertainty in the modelling. (four marks) (d) Outline two ways in which the consultant could improve their use of Monte Carlo simulation in this risk assessment. (four marks)

Explanation / Answer

1. Yes , I think the consultants are reasonable as in the month of Jan,Feb , March , April , may , that is summer season . The amount of average monthly steam flow is more in case after dam is constructed. The water stored in rainy season can be used during summers.

2. The uncertainty that can cause the streamline flow to below the certain level ,that can increase risk of certain sensitive species should be considered .

Failure of dam should also be considered .

Alternatives should be considered.If present , they should be applied .

Chances of flood ,should also be considered.

3. What percent of water should be stored in what month .?And how much should be allotted to environment flow is how decided , based on what criteria ?

What chances they took for dam construction failure , and on what basis ?

4. They can improve the risk assessment by -

Taking more no of simulations , that is not in months but may be in 15 days.

Certain factors that can cause major problem or threat can be given some more value points.

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