OPUS 4 | Universitätspublikationen

Value of river discharge data for global-scale hydrological modeling (2008)

Martin Hunger Petra Döll

This paper investigates the value of observed river discharge data for global-scale hydrological modeling of a number of flow characteristics that are e.g. required for assessing water resources, flood risk and habitat alteration of aquatic ecosystems. An improved version of the WaterGAP Global Hydrology Model (WGHM) was tuned against measured discharge using either the 724-station dataset (V1) against which former model versions were tuned or an extended dataset (V2) of 1235 stations. WGHM is tuned by adjusting one model parameter (γ) that affects runoff generation from land areas in order to fit simulated and observed long-term average discharge at tuning stations. In basins where γ does not suffice to tune the model, two correction factors are applied successively: the areal correction factor corrects local runoff in a basin and the station correction factor adjusts discharge directly the gauge. Using station correction is unfavorable, as it makes discharge discontinuous at the gauge and inconsistent with runoff in the upstream basin. The study results are as follows. (1) Comparing V2 to V1, the global land area covered by tuning basins increases by 5% and the area where the model can be tuned by only adjusting γ increases by 8%. However, the area where a station correction factor (and not only an areal correction factor) has to be applied more than doubles. (2) The value of additional discharge information for representing the spatial distribution of long-term average discharge (and thus renewable water resources) with WGHM is high, particularly for river basins outside of the V1 tuning area and in regions where the refined dataset provides a significant subdivision of formerly extended tuning basins (average V2 basin size less than half the V1 basin size). If the additional discharge information were not used for tuning, simulated long-term average discharge would differ from the observed one by a factor of, on average, 1.8 in the formerly untuned basins and 1.3 in the subdivided basins. The benefits tend to be higher in semi-arid and snow-dominated regions where the model is less reliable than in humid areas and refined tuning compensates for uncertainties with regard to climate input data and for specific processes of the water cycle that cannot be represented yet by WGHM. Regarding other flow characteristics like low flow, inter-annual variability and seasonality, the deviation between simulated and observed values also decreases significantly, which, however, is mainly due to the better representation of average discharge but not of variability. (3) The choice of the optimal sub-basin size for tuning depends on the modeling purpose. While basins over 60 000 km2 are performing best, improvements in V2 model performance are strongest in small basins between 9000 and 20 000 km2, which is primarily related to a low level of V1 performance. Increasing the density of tuning stations provides a better spatial representation of discharge, but it also decreases model consistency, as almost half of the basins below 20 000 km2 require station correction.

Selected Results from Socio-Ecological Participatory Situation Assessments in Two Sites in Central Northern Namibia (2008)

Jutta Deffner Patrik Klintenberg Clarence Mazambani Petra Moser-Norgaard Nantanga Komeine Mary Seely

Village-scale and Solar Desalination Technology Experience in Namibia (2008)

Detlof von Oertzen Robert Schultz

kurz und kn@pp news : Nr. 11 (2008)

* Preis für exzellente Lehre * Verordnungssicherheit bei niereninsuffizienten Patienten * Prof. Gerlach im Gesundheits-forschungsrat des BMBF * Gesundheit im Alter * DEGAM gegen IGeLn * Expertentreffen chronische Herzinsuffizienz

kurz und kn@pp news : Nr. 12 (2008)

* 1. Tag der Allgemeinmedizin in Frankfurt * Dosisanpassung bei Patienten mit chronischer Niereninsuffizienz * KoMed: Kommunikation im Medizinstudium * Prof. Dr. med. Jochen Gensichen an die Universität Jena berufen * Prof. Gerlach zum geschäftsführenden Direktor ZGW gewählt * Studie zur Sicherheitskultur:noch Praxen gesucht

kurz und kn@pp news : Nr. 13 (2008)

* Professionalisierung der Allgemeinmedizin * 42. Kongress der Deutschen Gesellschaft für Allgemeinmedizin und Familienmedizin (DEGAM) * Online-Eintragung für Studierende jetzt möglich * Opernkarten für Teilnehmer der PRoMPT-Studie * MultiCare: Multimorbiditätsmuster in der hausärztlichen Versorgung * Berliner Gesundheitspreis 2008: Gesagt ist nicht getan

kurz und kn@pp news : Nr. 14 (2008)

* Lothar Beyer-Preis für Frankfurt * Gut angekommen: 1. Frankfurter Tag der Allgemeinmedizin * Mitarbeiter/innen gesucht * EbM Frankfurt erhält Preis für junge Lehrende 2008 * Frankfurter Wissenschaftlerin goes Oxford * EGPRN – Europäisches Netzwerk allgemeinmedizinischer Forschung

kurz und kn@pp news : Nr. 11 [engl. Fassung] (2008)

* Prize for excellent teaching * Drug prescription safety and renal failure * Prof. Gerlach on the Health Research Council of the German Ministry for Education and Research * Health in Old Age * DEGAM against IGeLn * A Meeting of Experts on Chronic Heart Failure

kurz und kn@pp news : Nr. 13 [engl. Fassung] (2008)

* The Professionalization of General Practice * 42nd Congress of the DEGAM German Society of General Practice and Family Medicine * Online Registration for students now possible * Opera tickets for participants in the PRoMPT study * MultiCare: Multimorbidity patterns in General Practice * Berlin Health Prize 2008: Words are not enough

short @nd sweet news : Nr. 14 (2008)

* Lothar Beyer Award for Frankfurt * Well received: 1st General Practice Day in Frankfurt * Job Vacancies * EbM Frankfurt awarded Young Teachers prize for 2008 * Frankfurt Research Scientist goes to Oxford * EGPRN – European General Prac-tice Research Network

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