River discharge to the sea - Ísafjarðardjúp test area (83 catchments)
Method A, period 01/01/2023 to 31/12/2023
Export 07/10/2026. 

FILES
discharge_methodA_2023_isafjardardjup.csv   one row per outlet and day
discharge_methodA_2023_isafjardardjup.nc    the same, NetCDF (dimensions time x outlet)
outlets_methodA_2023_isafjardardjup.csv     one row per outlet

COLUMNS (CSV)
outlet_id              ID of the outlet point where the river reaches the sea (pointid of the drainage point)
catchment_id           HydroID of the catchment draining to that outlet (no river names in the layer yet)
latitude, longitude    outlet (drainage point) in WGS84, decimal degrees
catchment_area_km2     catchment area, computed in ISN93 (EPSG:3057)
date                   day (UTC), yyyy-mm-dd
discharge_m3s          daily mean discharge, no routing
discharge_routed_m3s   the same water through a linear reservoir, k = 0.85 (NOT calibrated);
                       the reservoir starts empty on the first day, so the first weeks are too low
carra_coverage         (outlets file) share of the catchment on CARRA cells with runoff data

METHOD
Q [m3/s] = (surface runoff + percolation) [mm/day] x catchment area [m2] / 86 400 000
Input: CARRA reanalysis, dataset reanalysis-carra-means, West domain, daily values, 2.5 km grid
(Copernicus Climate Change Service). Catchment value = mean of the grid cells weighted by the
area of each cell inside the catchment. No calibration, no correction factor.

COMMENTS
- One year and a test area of 83 catchments (2572 km2), not all of Iceland.
- Yearly volume against gauges (direct series): outlet_id 78: 29 % too low (365 days); outlet_id 83: 39 % too high (365 days).
  The errors are reported, not corrected.
- CARRA has no runoff data over sea cells. 4 catchment(s) have less than 95 % of their area
  on cells with data: outlet_id 8, 213, 231, 233. Their runoff comes from the covered part.
- Daily CARRA fluxes are available for 1990-1994 and from 2023; 2017 and 2018 are not available, but I might wrong. This is what I found so far.