उदयास्तमनेत्विंदोर्वर्द्धंत्यापो ह्रसन्ति च ।। अतो न्यूनातिरिक्ताश्च पक्षयोः शुक्लकृष्णयोः ।। ७१ ।।
At the time of rising and setting of the moon waters flow and ebb. Hence in the bright and dark halves the waters vary in quantity; they increase and decrease.