<p>Total cistern volume can be estimated by multiplying the depth of design storm the catchment area. <br>One millimeter of rain landing on 1 m<sup>2</sup> results in 1 L of runoff. <br> | <p>Total cistern volume can be estimated by multiplying the depth of design storm the catchment area. <br>One millimeter of rain landing on 1 m<sup>2</sup> results in 1 L of runoff. <br> |