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GRACE and GRACE-FO satellite missions provide important data necessary for temporal gravity field variation modelling. The main cause of Earth’s gravity field variations monitored by GRACE and GRACE-FO is the motion of Earth masses. To assess the ice mass variations, we have to correct the measured gravity signal for land hydrology variations and effect of post-glacial isostatic rebound. This paper describes the computational process of ice mass variations in Austfonna glacier ice cap. A total of 198 monthly GRACE and GRACE-FO global geopotential models, global hydrological model GLDAS NOAH and GIA model forced with ICE-5G global ice loading history were used to estimate the value of quadratic trend in terms of equivalent water height. Družicové misie GRACE a GRACE-FO nám poskytujú dáta vhodné na modelovanie tiažového poľa Zeme. Hlavným zdrojom variácií tiažového poľa zachytených misiami GRACE a GRACE-FO je pohyb zemských hmôt. Pre určenie variácií ľadovcových hmôt musíme zachytený gravitačný signál opraviť o kontinentálnu hydrológiu a efekt z postglaciálneho izostatického vyrovnania. Článok sa venuje popisu procesu výpočtu časových variácií kontinentálneho ľadovca Austfonna. Zo 198 globálnych geopotenciálnych modelov misií GRACE a GRACE-FO v kombinácii s hydrologickým modelom GLDAS NOAH a modelom postglaciálneho izostatického vyrovnania založeného na ľadovcovej histórii ICE-5G bol určený časový rad znázorňujúci zmeny kontinentálneho ľadovca Austfonna a jeho kvadratický trend v zmysle ekvivalentnej výšky vodného stĺpca.

Study region: The Rufiji basin, East Africa. Study focus: Rapid advances in global hydrological model (GHM) resolution, model features, and in situ and remotely sensed datasets are driving progress towards local relevance and application. Despite their increasing use, however, evaluation of local hydrological performance of GHMs is rare. In this paper, we examine the performance of a well-known GHM (LPJmL, recently modified to ∼9 km resolution) with and without modest steps to regionalise the model. We consider the Rufiji river basin, an economically important medium-size basin in eastern Africa. New hydrological insights for the region: Our results indicate that the unmodified GHM does provide a reasonable first approximation of spatial variability in mean flow conditions, but scores rather poorly on seasonal and inter-annual variability. For the model to achieve levels of performance indicators comparable with bespoke modelling, modifications to model inputs, additional runoff delay and wetland parameterization were required. The largest improvements are associated with adjustments in precipitation and enhanced runoff delay. With the modified version, as a proof of concept, we show that a well-known drying trend in a major tributary of the Rufiji can be explained by implementing irrigation abstractions in the model. Overall, the results suggest that with limited and fairly simple modification GHMs can be regionalised to allow their use for scenario testing and further exploration of key local processes in basins with limited observational data.

Study region: The Rufiji basin, East Africa. Study focus: Rapid advances in global hydrological model (GHM) resolution, model features, and in situ and remotely sensed datasets are driving progress towards local relevance and application. Despite their increasing use, however, evaluation of local hydrological performance of GHMs is rare. In this paper, we examine the performance of a well-known GHM (LPJmL, recently modified to ∼9 km resolution) with and without modest steps to regionalise the model. We consider the Rufiji river basin, an economically important medium-size basin in eastern Africa. New hydrological insights for the region: Our results indicate that the unmodified GHM does provide a reasonable first approximation of spatial variability in mean flow conditions, but scores rather poorly on seasonal and inter-annual variability. For the model to achieve levels of performance indicators comparable with bespoke modelling, modifications to model inputs, additional runoff delay and wetland parameterization were required. The largest improvements are associated with adjustments in precipitation and enhanced runoff delay. With the modified version, as a proof of concept, we show that a well-known drying trend in a major tributary of the Rufiji can be explained by implementing irrigation abstractions in the model. Overall, the results suggest that with limited and fairly simple modification GHMs can be regionalised to allow their use for scenario testing and further exploration of key local processes in basins with limited observational data. Keywords: LPJmL, Global hydrological model, Regionalization, Rufiji, Irrigation abstractions, Water resources, Stiegler’s Gorge