If there is shortage of water and we store water 4-5 days and it is stagnant water.so if we perform ghusl in this stagnant water without change in colour,smell, taste is my ghusl is valid

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

This stagnant water is ritually pure and valid for purification; it is permissible for you to make Ghusl with it. However, it is incumbent on the one using that water in making Ghusl to take from it without immersing his body in it. That is because many scholars view that immersing the body into such water makes it lose the quality of being Tahoor, i.e. it becomes pure in itself but no longer valid for purification. This applies when the amount of water is small, being less than the volume of two Qullahs (about 200 liters).

A group of competent researching scholars, like Shaykh Ibn ‘Uthaymeen, however, believe that immersing the body into such water does not cancel its validity for purification. However, staying away from this scholarly difference in opinion is more cautious and prudent in terms of clearing one's liability. Therefore, whoever wants to perform Ghusl with this water should take from it but not immerse his body in it, as we have mentioned earlier.

Allah Knows best.