Answer:
![t = 0.75 \ hr = 0.75 *60 = 45 \ minutes](https://img.qammunity.org/2021/formulas/physics/high-school/c1or7ird1evnsrj3lz6wb9ltpc12zdef8m.png)
Step-by-step explanation:
From the question we are told that
The hydraulic conductivity is
![Ks = 10\ mm/hr](https://img.qammunity.org/2021/formulas/physics/high-school/23qskpss7cubs658qx31z4mjx3k5a0q371.png)
The effective matrix potential
![Ns = 20 \ mm](https://img.qammunity.org/2021/formulas/physics/high-school/1i0ip5idsa4v816c1xwy53ytye1p5a48d3.png)
The intensity of rainfall is
![I = 30 \ mm/hr](https://img.qammunity.org/2021/formulas/physics/high-school/ecxys2rc7sqvzo186apo7cnia0iobip5is.png)
The runoff rate
![R = 15 \ mm/hr](https://img.qammunity.org/2021/formulas/physics/high-school/vooj5wayin1plejyc3dh0ff5v4f8mi6lkr.png)
Generally the run off rate is mathematically represented as
![R = (I - Ks) t](https://img.qammunity.org/2021/formulas/physics/high-school/lw91638p0my6wzeu4xlt5x4vfud0yi0kqy.png)
Here t is the amount of runoff generated
=>
![15 = (30 - 10) t](https://img.qammunity.org/2021/formulas/physics/high-school/qf3bft3wuc3fmmn7h3q1yrhdtmhflc3dco.png)
=>
![t = 0.75 \ hr](https://img.qammunity.org/2021/formulas/physics/high-school/tkm82cq5vg6x7k20z75z4yg2capganwxp8.png)
converting to minutes
![t = 0.75 \ hr = 0.75 *60 = 45 \ minutes](https://img.qammunity.org/2021/formulas/physics/high-school/c1or7ird1evnsrj3lz6wb9ltpc12zdef8m.png)