Based on his calculation of the need for water at 1,000 cubic meters per rai in the dry season, the cultivation area that makes up the second part, 9 rai in all, would need about 9,000 cubic meters of water. He also took into consideration the evaporation of water from the pond in the dry season, with the water level reduced by about 1 centimeter a day. With an average of 300 days without rain in a year, the water level in the pond would be reduced by three meters. Therefore, the pond must be large enough to ensure that there is enough water.