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In the framework of the WISH key program, several H2O (E_u>190 K), high-J CO,[OI], and OH transitions are mapped with PACS in two shock positions along thetwo prototypical low-luminosity outflows L1448 and L1157. Previous HIFI H2Oobservations (E_u=53-249 K) and complementary Spitzer mid-IR H2 data are alsoused, with the aim of deriving a complete picture of the excitation conditions.At all selected spots a close spatial association between H2O, mid-IR H2, andhigh-J CO emission is found, whereas the low-J CO emission traces eitherentrained ambient gas or a remnant of an older shock. The excitation analysisat L1448-B2 suggests that a two-component model is needed to reproduce the H2O,CO, and mid-IR H2 lines: an extended warm component (T~450 K) is traced by theH2O emission with E_u =53-137 K and by the CO lines up to J=22-21, and acompact hot component (T=1100 K) is traced by the H2O emission with E_u>190 Kand by the higher-J CO lines. At L1448-B2 we obtain an H2O abundance(3-4)x10^{-6} for the warm component and (0.3-1.3)x10^{-5} for the hotcomponent; we also detect OH and blue-shifted [OI] emission, spatiallycoincident with the other molecular lines and with [FeII] emission. Thissuggests a dissociative shock for these species, related to the embedded atomicjet. On the other hand, a non-dissociative shock at the point of impact of thejet on the cloud is responsible for the H2O and CO emission. The other examinedshock positions show an H2O excitation similar to L1448-B2, but a slightlyhigher H2O abundance (a factor of 4). The two gas components may represent agas stratification in the post-shock region. The extended and low-abundancewarm component traces the post-shocked gas that has already cooled down to afew hundred Kelvin, whereas the compact and possibly higher-abundance hotcomponent is associated with the gas that is currently undergoing a shockepisode.

Herschel PACS observations of shocked gas associated with the jets of L1448 and L1157