Changes in the Air Temperature Conditions of the Northwest Shore Area of Lake Nakaumi Caused by the Construction of the Closing Dikes around the Land Draining Site

Abstract

The reclamation works in the northwest part (1, 689 ha) of Lake Nakaumi, which is a brackish lake with an average depth of 5.4 meters, have been in progress. We have been making air temperature observations in the surrounding area for the past ten years to study the effects of largescale land draining on the air temperature conditions in the vicinity. In the present paper, the effects caused by the construction of the closing dikes around the land draining site have been discussed.
The annual mean temperature level at Station located on the shore (Fig. 1) after the construction of the dikes is about 0.5°C higher than before the construction. The levels of the pentad minimum and maximum temperatures are also found to have risen almost all the year round, but the degrees of the rise vary from season to season.
The closing dikes cut off the inflow of relatively low-temperature freshwater from the basin resulting in the a rise in the surface water temperature, which must be responsible for the rise in the air temperature of the surrounding area.