Adding monthly evaporation and rainfall

In this step, we will add the the Evaporation and Precipitation rates (mm/day). Internally the reservoir multiplies the real-time Reservoir area by the Evaportion.

The Evaporation can be defined by a parameter or a scalar. For example, a time series can be used that is correlated to the flow scenario time series. However in this case, we will use a Monthly profile parameter which assigns a different value to each month in the year.

1. Select the reservoir and edit the Evaporation attribute.

2. WaterStrategy has a Json editor for a Monthly profile parameter. To use it, In the options tab select PYWR_MONTHLY_PROFILE.

3. In the Monthly Profile tab, enter the evaporation rates in the table below:

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Evaporation (mm/day)	2.70	4.02	1.45	1.98	0.98	0.10	0.04	0.03	0.04	0.48	1.14	2.45

4. Follow the same steps for the Rainfall attribute using the table below the figure.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Precipitation (mm/day)	4.91	2.33	1.24	2.30	0.39	0.01	0.01	0.00	0.01	0.48	1.76	2.23

5. Finally set the 'Evaporation Penalty' to -2000 and the Evaporation Unit Conversion on the reservoir node to 0.001.

The highly negative Evaporation Penalty of -2000 is higher priority than either the reservoir and any other nodes in the system. This ensures that evaporation outflow is met first before any managment rules are implemented.

The Unit Conversion allows the model to correctly convert the evaporation in mm/day and reservoir area in Km2 to the correct flow units in the template which are Mm3/day

6. Run this scenario and compare the simulated volume against the 'With treatment losses' scenario.

Evaporation is shown to result in a decrease in reservoir levels during droughts. Precipitation additions do not compensate for the losses.

Exercise

1. One of the domestic interventions in the Botswana Intervention Prioritization project was the installation of Floating Solar Panels. The solar panels would cover a portion of the reservoir and reduce its evaporation.

In new scenarios, implement floating solar where 5, 10 and 20% of the reservoir is covered by solar panels.

Hint: To model the implementation of solar panels, reduce the area of the reservoir by the relevant percent in the Interpolated Area Parameter Json.