Estimating evaporation from reservoirs: accepted methods Which of the following methods are used in practice to estimate reservoir evaporation rates for water balance and design?

Introduction / Context:
Evaporation is a critical loss term in reservoir operation and design. Its assessment affects yield analysis, drought planning, and salinity management. Multiple complementary methods exist, each with different data needs and accuracy levels.

Given Data / Assumptions:

• Site has meteorological records (temperature, humidity, wind, radiation) and storage measurements.
• Calibration from local pan coefficients or energy balance may be available.

Concept / Approach:

Pan method uses measured pan evaporation times a pan coefficient to approximate lake evaporation. Empirical formulae estimate evaporation from climate variables. Storage equation uses reservoir water-balance closure (inflows, outflows, storage change, rainfall) to back-calculate evaporation. Energy budget evaluates latent heat flux from the surface energy balance.

Step-by-Step Solution:

Verification / Alternative check:

Comparing monthly totals from pan-based estimates and storage equation often reveals biases, leading to adjusted coefficients.

Why Other Options Are Wrong:

• Each of (a)–(d) is valid; choosing any single one omits accepted practice.

Common Pitfalls:

• Using pan data without local calibration.
• Ignoring rainfall on the reservoir surface in storage equation calculations.

Final Answer:

All the above.