Types of Diurnal Variation of Water Temperature in the Irrigation Canals in the Lower Reach of the Natori River

Abstract

Through the observation of water temperature in the irrigation canals, following types were found in the diurnal variations of water temperature.
1) The diurnal variations of water temperature at observating points were classified into six types.
Type I : Rise and fall of water temperatures are smooth and its rise is quick.
Type II : Rise and fall are smooth too, but its rise is slow.
Type III : The rise of temperature has one step.
Type IV : The type with two peaks.
Type V : The fall of water temperature has one step.
Type VI : Rise and fall are smooth and quick, besides in this type there is a period when the temperature stays without a change for several hours in early morning.
2) Presumably, these types are connected to make a cyclic ring of I-II-III-IV-V-I.
3) This cycle was caused by diurnal and nocturnal variations of water temperature flowing in the canals.