gen-define-reservoir-storage-and-give-one-short-worked-example-34e9

Define reservoir storage and give one short worked example.

# Reservoir Storage ## Definition **Reservoir storage** is the volume of water held (or that can be held) in a reservoir at any given time. It's typically measured in cubic meters (m³), acre-feet, or million cubic meters (MCM). Storage varies between: - **Dead storage** - volume below the lowest outlet (unusable) - **Active/live storage** - usable water between minimum and maximum operating levels - **Total storage** - entire volume up to the maximum water level --- ## Worked Example **Problem:** A reservoir has the following characteristics: - Reservoir surface area at normal level: 5 km² - Water level on Jan 1: 150 m - Water level on Jan 31: 148 m - Monthly inflow: 12 MCM - Monthly water supply release: 18 MCM **Find the evaporation and seepage losses.** **Solution:** Using the water balance equation: $$\text{Storage change} = \text{Inflow} - \text{Outflow} - \text{Losses}$$ Change in storage = Area × Change in depth $$= 5 \times 10^6 \text{ m}^2 × (148 - 150) \text{ m}$$ $$= 5 \times 10^6 × (-2) = -10 \times 10^6 \text{ m}^3$$ $$= -10 \text{ MCM}$$ Applying water balance: $$-10 = 12 - 18 - \text{Losses}$$ $$\text{Losses} = 12 - 18 + 10 = 4 \text{ MCM}$$ **Answer:** Evaporation and seepage losses = **4 MCM**