**-d**- Debug with intermediate maps
**--overwrite**- Allow output files to overwrite existing files
**--help**- Print usage summary
**--verbose**- Verbose module output
**--quiet**- Quiet module output
**--ui**- Force launching GUI dialog

**elevation**=*name***[required]**- Name of input elevation raster map
**discharge**=*name***[required]**- Name of input river discharge raster map [m3/s]
**rivers**=*name*- Name of input vector map
- Name of river network input vector map
**lakes**=*name*- Name of input vector map
- Name of lakes input vector map
**threshold**=*string***[required]**- Minimum size of exterior watershed basin
- Default:
*0* **basins**=*name*- Name of basin map obtained by r.watershed
**stream**=*name*- Name of stream map obtained by r.watershed
**output**=*name***[required]**- Name of output vector map with basin potential [MWh]

If there are already existing plants, the function computes the potential installed power in the available parts of the rivers.

This module returns two output vector maps with the available river segments and the optimal position of the plants with their potential maximum powers, intakes and restitutions.

In this module the output is the theoretical maximum hydropower energy that can be converted in the ideal case without considering the efficiency of energy transformation.

You can optionally add vector maps of existing river networks and lakes that will be considered in the calculation and make the output more realistic.

Instead of the minimum size of the exterior watershed basin you can also enter the basin and stream maps created by r.watershed.

In real life this situation does not arise, because of environmental flows, other water uses and economic cost analysis.

The underlying methods of calculation explained below are based on the considerations and formulas used in the article "A GIS-based assessment of maximum potential hydropower production in La Plata Basin under global changes" written by M. Peviani, I. Popescu, L. Brandimarte, J.Alterach and P. Cuya.

The maximum potential hydropower at subbasin scale can be computed as the sum of two components:

- upstream subbasin potential - subbasin own potential

According to the general schematization in the figure below, point A is the closure point of the upstream subbasins (named UPSTREAM 1, UPSTREAM 2 and UPSTREAM 3).

The three rivers belonging to the three upstream basins merge into the common river of the downstream basin in point A (named Upstreamclosure point).

The downstream basin is bounded by the two closure points A and B.

The scheme divides the subbasins in upper portions, whose energy production is only given by their own potential and a lower portion, whose energy production is the sum of the two components, own potential and the potential given by the flow coming from the upper portions.

Subbasin scheme to calculate maximum potential hydropower

The maximum potential hydropower for the upstream subbasins is given by the energy formula applied to the upstream inflows:

where conv is the adimensional conversion factor to calculate energy in GWh (conv = 0.00876);

g is a gravity constant (9.81 m/s^{2});

η is the overall electrical efficiency;

Q_{up_hydro}is the mean annual discharge at the closure section for the upstream subbasin;

H_{mean}is the mean elevation of the upstream subbasin calculated from the hypsographic curve, using the statistical tool of Arc-GIS;

H_{closure}is the elevation at the closure point (point A in the figure);

where Q_{aff}is the afferent discharge (own lower subbasin discharge). The afferent discharge is the difference of the discharge observed at the closure section (point B in the figure) and the sum of the upstream discharges;

H_{mean}is the elevation of lower subbasin;

H_{closure}is the elevation at closure point (point B in the figure);

where Q_{up_hydro}is the sum of the mean annual discharges coming from the upstream subbasins;

H_{up_closure}is the elevation at the upstream closure point (point A in the figure);

H_{closure}is the elevation at closure point (point B in the figure);

This example is based on the case-study of the Gesso and Vermenagna valleys located in the Piedmont Region, in South-West Italy, close to the Italian and French border.

In the map below you can see the input files elevation and natural discharge.

input raster map with elevation and natural discharge

For a faster run of this example, the input maps elevation and discharge are limited to the section that can be modified by r.green.hydro.theoretical using the code

r.mask vector=boundary.

To create the map of this example, you can type in the following code in the command console or if you prefer you can only type in the main function r.green.hydro.theoretical in the console and specify the other parameters of the code like elevation or discharge by using the graphical user interface.

r.green.hydro.theoretical elevation=elevation discharge=naturaldischarge rivers=streams lakes=lakes basins=basin stream=stream output=out

In the map below, you can see the output vector map with the basin potential.

output vector map with basin potential

r.green.hydro.delplants

r.green.hydro.optimal

r.green.hydro.recommended

r.green.hydro.structure

r.green.hydro.technical

r.green.hydro.financial

Available at: r.green.hydro.theoretical source code (history)

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