The water level and temperature properties for the cooling system of potassium titanyl phosphate laser systems were observed. The middle point of the GMR-SV magnetoresistance curve is set in the neighborhood of high magnetic sensitivity (2.8 %/Oe). The experimental results for resistance dependence on water height and temperature showed linear regions with rates of 0.4 Ω/mm and 0.1 Ω/°C, respectively. The proposed results were found to be for adjusting the water level and temperature in the laser cooling system.