r.green.hydro.discharge - GRASS GIS manual

NAME

r.green.hydro.discharge - Calculate average natural discharge and minimum flow following regional law an

KEYWORDS

SYNOPSIS

r.green.hydro.discharge

r.green.hydro.discharge --help

r.green.hydro.discharge [-dfp] [q_spec=name] q_river=name [k_b=name] [k_n=name] [rain=name] [k_matrix=name] [m_matrix=name] [a_matrix=name] [mfd=name] [a_river=name] elevation=name [river=name] [lakes=name] streams=name [corr_fact=name] [env_area=name] threshold=float [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-d: Debug with intermediate maps
-f: compute the discharge in the river with q_spec=flow map
-p: compute the discharge in the river with q_spec computed as see manual
--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

Parameters:

q_spec=name: Name of the specific discharge [l/s/km2]
q_river=name [required]: Name of raster map with the discharge along river [m3/s]
k_b=name: Name of raster map with kb parameter
k_n=name: Name of raster map with kn parameter
rain=name: Name of the specific with rain [mm]
k_matrix=name: Name of k area map with k parameter
m_matrix=name: Name of M area map with M parameter
a_matrix=name: Name of A area map with A parameter
mfd=name: Name of raster map with minimum flow along the river [m3/s]
a_river=name: Name of raster map with area of the basin along the river [m2]
elevation=name [required]: Name of input elevation raster map
river=name: Name of river network; Or data source for direct OGR access
lakes=name: Name of lakes network; Or data source for direct OGR access
streams=name [required]: Name of the new stream network
corr_fact=name: Name of corrective factors area map for environmental flow
env_area=name: Name of area with environmental restriction
threshold=float [required]: Minimum size of exterior watershed basin; Default: 100000

DESCRIPTION
NOTES
EXAMPLE
SEE ALSO
REFERENCE
AUTHORS

DESCRIPTION

r.green.hydro.discharge calculates the average natural discharge and the minimum flow discharge according to regional laws.

NOTES

The natural discharge is the discharge of the streams which doesn't consider the existing power plants and the other structures exploiting the water of the river.
The Minimal Flow Discharge (MFD) is the amount of water which has to remain in the river to preserve the ecosystems. The legislation differs in each region. The MFD can be considered as a percentage of the current discharge, which is the discharge of the river considering the structures exploiting the water. The current discharge is often considered as the mean annual discharge.

However, a percentage of the current discharge cannot define precisely the MFD and each region has a different method to define it. For the moment, this module only considers the legislation applied on Piave basin in the Veneto region. New tabs with the legislation of other regions could be added.

The module computes two raster maps : the natural discharge and the MFD. On Piave basin, the natural discharge can be computed thanks to the input raster map with the values of specific discharge, and the MFD is calculated thanks to this formula :

Q_MFD = ( K_b + K_n ) * 177 * S^0.85 * Q_spec * 10^-6

where K_b is the biological criticality index,
K_n is the naturalistic criticality index,
S is the catchment area, in km²,
Q_spec is the specific flow-rate per unit area of the catchment, in l/(s.km²)

K_b is typically within the range of 1-1.6; higher values are chosen for a river whose aquatic ecosystem is considered to be of a particular environmental value.
K_n is typically within the range of 0-0.6; higher values of such index are used for basins having a particular naturalistic value, for instance national parks.
The values of K_b and K_n are imposed by the Piave River Catchment Authority (PRCA). They have different values depending on homogeneous segments which can be found in a table made by the PRCA. Also the values of Q_spec depend on the area and are available in such a table.

Thanks to three raster maps respectively with the values of K_b, K_n and Q_spec, and also the elevation raster map and the streams vector map, the module creates the two raster maps with the values of MFD and average natural discharge.

EXAMPLE

This example is based on the case-study of Mis valley in Belluno province, Veneto, Italy.

Here is the map of the Mis valley with colored areas to define the K_n, K_b and Q_spec values. input

Picture which gathers the input raster maps with K_n, K_b and Q_spec values

According to the legislation for the Piave basin explained above, the legal values for the Mis valley are :
K_n = 0.4 in the whole region (yellow and red zones)
K_b = 1.4 in the yellow zone and 1.6 in the red zone
Q_spec = 44 l/(s.km²) in the yellow zone and 43 l/(s.km²) elsewhere (red and white zones)

These values are put in three different raster maps : q_spec, k_b and k_n.
Here is the code used to create the raster maps with the MFD and the natural discharge. The basins are considered with a threshold of 10000 m.

r.green.hydro.discharge q_spec=q_spec output_q_river=discharge k_b=k_b k_n=k_n output_mfd=mfd elevation=elevation output_streams=streams threshold=100000

The following picture gathers the two output raster maps mfd and discharge which look like each other (yellow background with colored points following the river and containing the values of discharge). For a better understanding, the following picture also shows the border of the Mis valley and the streams.

output

Picture which gathers the output raster maps with valued of MFD and natural discharge, also showing the vector maps with the borders and streams of Mis valley

The white point is queried in GRASS to know the values of MFD and natural discharge. The following picture shows these values in m³/s.

table

Values of MFD and natural discharge (in m³/s) at the white point

REFERENCE

Allegato alla delibera n. 4/2004 del Comitato Istituzionale del 3 marzo 2004
Piano stralcio per la gestione delle risorse idriche del bacino del Piave - Misure di Salvaguardia
from Autorità di bacino dei fiumi Isonzo, Tagliamento, Livenza, Piave, Brenta-Bacchiglione

AUTHORS

Giulia Garegnani (Eurac Research, Bolzano, Italy), Sara Biscaini (University of Trento, Italy), Manual written by Julie Gros.

SOURCE CODE

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