Official Norwegian Hydro Reservoir Capacity Changed

hydrology normals and forecasts
April 8, 2019Tor Reier Lilleholt

From Monday 8th of April 2019, The Norwegian Water Resources and Energy Directorate (NVE) will change their reporting of Norwegian hydro reservoirs. Learn what that means for you.

Instead of reporting measured data, which stands just for 95% all hydro reservoirs in Norway, NVE will start reporting on actual capacity.  As a consequence, the actual hydro production capacity is increasing from 82.2 TWh to 86,7 TWh and will result in a shift in all historical statistics. We in Wattsight have commented on the wrong use of reports for many years and have based on a different reporting for more than 20 years.

Numbers Not Updated Correctly

NVE has reported official hydro reservoirs based on an incomplete measurement for more than 20 years. Just a couple of years ago, the  Norwegian Water Resources and Energy Directorate did a necessary update on expansions in production capacity and new dams. However, even without building new dams, changes in the production system might change the capacity in the hydro reservoir as the water can be used in a better way. To our knowledge, all these numbers have been not updated sufficiently for several years, and we in Wattsight had to use not official actuals to report capacity.

Strong Impact on Inflow and Snow Modelling

The official inflow numbers for Norway will be calculated based on the change in hydro reservoirs and the measured production. If one increases the capacity in the hydro reservoirs used for reporting with 5%, one might say that all historical data has been reported with a 5% miscalculation. In the filling season, the official inflow from NVE is always reported too low, and vice versa in the winter time. A change in % for a higher capacity means more inflow with production as constant. For a whole melting season from week 15 to week 35, we have 86 TWh inflow in Norway, and based on this 5% miscalculation means 4-5 TWh wrong reporting of snow if you don’t compensate for this. 

Unique Wattsight Hydrology Approach

We in Wattsight are proud to have foreseen this issue and have used the total capacity numbers from the early morning. For more than 20 years, we have seen this reporting as a wrong way of describing the inflow. We have also addressed this topic to NVE over the years. Therefore, all our statistics have been updated with adjusted official inflow numbers, and this has been the basis for all snow models. The remaining hydro reservoir capacity has been changed with the same changes in % as the measured ones to find the correct inflow. 

We in Wattsight do not need to apply any changes to this other than start using new official inflows which are more accurate than old official statistics. There will be no need for adjusting this weekly numbers by Wattsight any more as NVE will give better possible official inflow number from this week onwards.

The deviation has often been a source to difficulties comparing Wattsight’s snow reservoir with other numbers in the market which not use our principles in their calculation. We calculate lower inflow during the snow accumulation and higher inflow during the melting or filling season.

Do you have questions what that means for you? Contact Head of Analysis, Tor Reier Lilleholt.