Diurnal Temperature Cycles in Shallow Water Pools

The growth and development of cold-blooded water organisms is strongly affected by temperature. In many ecological models, air temperature or "bulk water" temperature is used as an input parameter. However, organisms that live close to the water surface in shallow waters, such as larvas of mosquito species, are exposed to temperatures, which differ considerably from the air or bulk water temperature. The objective of the present research is, first, to develop a simple one-dimensional model to simulate the temperature profile within small water bodies. The second goal is to conduct outdoor experiments to estimate the model input parameters and to verify the model for different shallow water pools. The model simulations as well as the measurements show that during daytime strong temperature stratification occurs in the water. This stratification is strongly dependent on wind speed and is dependent on the vegetation of the surrounding environment of the water body. Throughout the night, however, a well-mixed layer develops growing from the water surface. Qualitatively, the model simulations agree with the measurement results. Quantitatively, however, it appears that for not too small water bodies (d > 2m) the one-dimensional model performs well and for small water bodies (d < 1m) the model is too simple to simulate the temperature well. Then the shape of the boundaries of the water body plays an important role in the exchange processes between the water body and the underlying sediment. Also it appears that the temperature behavior is very sensitive to the extinction coefficient for short wave radiation, which is closely related to the suspension of fine particles in the water.