TIMING OF WATER MEASUREMENTS
• Water bodies are some of the most dynamic features on earth, and certain aspects of them may change in a day, or even a few hours.
• The rate of change in water level will vary with the area and volume of the water body and the shape of the basin containing it.
• Sediment concentrations—and algae—are not uniformly distributed in lakes and reservoirs, and significant areal variation in concentration is often present.
• Currents in a lake can be due to wind and stream inflow, producing a visible pattern in the suspended sediment that changes continuously.
• All these variables make field work on water bodies highly time dependent, and may require making observations and taking samples at the exact time of an imaging overflight.