River discharge to the sea - whole of Iceland, catchment layer v0 (EU-Hydro basins to the sea)
Method A, period 01/01/2023 to 31/12/2023
Created 14/10/2026. PRELIMINARY.

FILES
discharge_methodA_2023_iceland_v0.csv   one row per outlet and day
discharge_methodA_2023_iceland_v0.nc    the same, NetCDF (dimensions time x outlet)
outlets_methodA_2023_iceland_v0.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           ID of the catchment draining to that outlet (EU-Hydro H1_ID without 'IC0H'); = outlet_id
river_name_vi, wfd_code, name_source, outlet_source   (outlets file) indicative river name, VI WFD code, how found
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.

LIMITS
- One year, 622 catchments draining to the sea (102642 km2): EU-Hydro
  drainage basins (iceland_eudem2_basins_h1, Copernicus), version 0, not edited. 10 inland basins without
  contact with the sea were merged into a neighbouring basin (column merged_inland of the catchment layer).
- Yearly volume against gauges (direct series): gauge V38 (LamaH-Ice catchment above the gauge): 32 % too low (365 days); gauge V448 (LamaH-Ice catchment above the gauge): 18 % too low (365 days); gauge V148 (LamaH-Ice catchment above the gauge): 5 % too low (365 days).
  The errors are reported, not corrected.
- CARRA has no runoff data over sea cells. 64 catchment(s) have less than 95 % of their area
  on cells with data: outlet_id 100003, 100007, 100016, 100020, 100042, 100051, 100052, 100054, 100057, 100060, 100073, 100077, 100088, 100095, 100105, 100116, 100125, 100167, 100169, 100180, 100181, 100204, 100207, 100219, 100221, 100229, 100238, 100239, 100268, 100270, 100273, 100283, 100290, 100300, 100319, 100326, 100327, 100335, 100339, 100356, 100362, 100399, 100401, 100405, 100412, 100428, 100433, 100440, 100455, 100458, 100480, 100483, 100487, 100492, 100493, 100515, 100547, 100550, 100554, 100558, 100583, 100584, 100585, 100597. Their runoff comes from the covered part.
- Outlet = EU-Hydro river mouth of the longest river in the catchment, else a point on its coast.
  outlet_id = catchment_id. River names (outlets file) are indicative, from the VI WFD river layer.
- Daily CARRA fluxes are available for 1990-1994 and from 2023; 2017 and 2018 are not available
  in this dataset at present.