  A fully renewable European power system comes with a variety of problems.
Most of them are linked to the intermittent nature of renewable generation from
the sources of wind and photovoltaics. A possible solution to balance European
generation and consumption are European hydro power with its seasonal and North
African Concentrated Solar Power with its daily storage characteristics. In
this paper, we investigate the interplay of hydro and CSP imports in a highly
renewable European power system. We use a large weather database and historical
load data to model the interplay of renewable generation, consumption and
imports for Europe. We introduce and compare different hydro usage strategies
and show that hydro and CSP imports must serve different purposes to maximise
benefits for the total system. CSP imports should be used to cover daily
deficits, whereas hydro power can cover seasonal imbalances. If hydro is used
in a "Hydro First" strategy, only around one quarter of North African Solar
Power could be exported to Europe, whereas this number increases to around
60\%, if a cooperative hydro strategy is used.
