Impact of irrigation on the hydrological cycle in the Mediterranean basin French Ministry for Higher Education and Research Grants Supervisor: Jan Polcher & Thomas Arsouze PhD Student: Trung Nguyen Quang The 1 st thesis committee meeting (Tuesday, 13 October 2015) ● The importance of riverine discharge into the Mediterranean ● Using HydroSHEDS data ● Routing scheme in ORCHIDEE ● Primary experiences with Madagascar’s domain

Why: Irrigation and hydrological cycle in the Mediterranean basin ? CEFREM database (Ludwig et. al, 2009) Global Map of Irrigation Areas (FAO) J. Margat, 2008 Irrigation

“The big picture” ➢ Simulation using ORCHIDEE and evaluation flows by comparing with observations ➢ Improving the representation of irrigation and dams in ORCHIDEE ➢ Various rivers flow scenarios over the period ➢ Simulation of ocean circulation (NEMO) using the different scenarios for river flows. ➢ Quantify the impact of river discharge changes on trends in salt and temperature.

Using HydroSHEDS data ● Hydrological data and maps based on SHuttle Elevation Derivatives at multiple Scales [Lehner, B., Verdin, K., Jarvis, A. (2006)] ● ~ 1 km resolution ( degree or 30 arc-second) Direction of flow from each box (trip) 138W – 180E ; 56S - 62N Basin number (IDs) for each grid box (basin) Digital elevation model (orog) 145W – 180E ; 56S - 60N Others data set: ● Global Lakes and Wetlands Database [Lehner, B. and Döll, P. (2004)] ● Relief of the surface of the Earth (etopo20.nc) [Smith, W.H.F., and D.T. Sandwell. (2004)] ● UN Land Cover Classification System (LCCS) (300 m resolution) [*] * What is trip ?

Using HydroSHEDS data ➢ Make verification: ● Checking the homogeneity between trip, basin and orog ● Follow river flow to: ● Each point has “outflow” point: a lake (trip=97), ocean (trip=98 or 99) ● Calculate flow accumulation ● Basin ID = 0 and have same “outflow” ● Calculate the distance to the outflow point of each point ● Calculate river length ● Calculate height difference between the two grid boxes ● Check point with trip = 97: compare with GLWD (*) ● Compare flow accumulation of points with trip = 99 (main outflow of river) and trip = 98 (coastal flow) and make some statistic (**)

Using HydroSHEDS data ➢ For Mediterranean: Calculate the distance to the outflow point of each point

Routing scheme in ORCHIDEE From slides of Matthieu GuimberteauMatthieu Guimberteau

Routing scheme in ORCHIDEE From slides of Matthieu GuimberteauMatthieu Guimberteau How many basins?

Routing scheme in ORCHIDEE

● What parameter? Experience design Name (unit)DescriptionTested values nbasmax (-)The maximum number of basins we wish to have per grid box (truncation of the model) 1, 2, 3, 5, 7, 10, 20, 25, 30, 50, 100, 200, 300, 500 dt_routing (s)Routing time step3600, 7200, resolution (km)10, 20, s7200 s s Theoretical runoff & drainage (During 03 days: one kg/m^2d divided up in runoff and drainage) Routing time step: 24h (~50 km) => 1h (<25km)

● Improved water residence index (by Agnès’ idea): “Topoindex” OLD NEW

Number of cascade should be care?: Cascade Compensate? [Gong et al., (2009)] 5 km 10 km 25 km 16 km 5 km 25 km

New formula of calculating outflow (with Agnès’ idea) Calculation of outflow OLD NEW Forcing with ORCHIDEE output: average runoff & drainage of Outflow from the reservoir OLD: Q=V*[dt_routing/86400/T] NEW: Q=V*[1-exp(-dt_routing/86400/T)]

● Routing time step ● New topoindex ● Forcing with ORCHIDEE output ● Forcing with 33 years ● Move to Mediterranean Some remarks Thank you for your attention