Why does the amount of water that flows in a river change during the year?

There are multiple factors that influence the amount of water that flows in a river.
1. A factor upstream like rain can cause the water level downstream to rise for a short period in time.
2. A blockage in a runoff stream can cause the main rivers water level to rise due to the lack of available runoff path for the water to take.
3. Also the melting of snow can cause the water level to rise as well.

the glands which are associated with each description is given below:

pancreas - is an endocrine and exocrine gland that secretes juices with enzymes for digestion. salivary glands- with protection and digestion in the mouth. liver- secretes bile for digestion.   lachrymal glands - secrete tears to moisten eyes and protect them from particles and infection.   sweat gland -regulates water, salt, and temperature. oil glands - to form a protective barrier on the skin.   goblet cells - secrete mucus for protection.

4, two dominant and two recessive