3.4.1. Consumer Daily Irrigation Demand Submodel

The consumer daily demand volume, *D I*, is calculated using the outdoor water demand model [88].

$$DI = \frac{f \times L \times ((k \times ET) - r)}{days} \tag{8}$$

where *f* is an irrigation factor indicating frequency of watering; *L* is the irrigable lawn area (m2); *k* is a crop coefficient; *ET* is evapotranspiration (mm/month); *r* is effective rainfall (mm/month); *days* is the number of days per month. Effective rainfall represents the precipitation that penetrates the soil and thereby reduces the water demand of plants. It is calculated as a function of total measured monthly rainfall *Pmonth* (mm/month) [88], as:

$$r = \begin{cases} \begin{array}{l} P\_{month} \\ 0.504 \times P\_{month} + 12.4 \end{array} & \text{if } 25 \le P\_{month} \le 152 \text{ mm} \end{cases} \tag{9}$$

The monthly demand value is converted and reported as a daily demand. The irrigation factor (*f*) is set at 1.0, because it is assumed all households that opt to connect to the system are frequent irrigators. The crop coefficient (*k*) is set as 0.7 to represent lawn. The value of *L* (irrigable lawn area) is calculated as

$$L = \left(\frac{1}{\rho} - A\right) \times \mathcal{U} \tag{10}$$

where the household density is *ρ* (unit per m2), roof area is represented as *A* (m2), and the ratio of unpaved land is *U* (dimensionless).
