Grouping and summing of dataset

[jef]

I have this dataset that I imported with pandas:

Output:
Date           Hour    Water
2020-01-01     2       5
2020-01-01     3       45
2020-01-01     4       63
2020-01-01     7       0
2020-01-01     24      35
2020-01-02     1       25

I want to total individual instances of the number of hours and liters. Each "hour" represents an hourly interval on my measuring device. Each "water" is the number of liters of water that flowed through the device in that hour. Thus the desired output is:

Output:
Start date    Start hour   Hours Elapsed    Water
2020-01-01    2            3                113
2020-01-01    24           2                60

If there are missing rows of dates/hours or if there is a row where water=BLANK or water=0, we should skip those.

Whats the easiest way to add this up?