hydrograph needs to accept xarray objects as inputs

[RolfHut]

Current implementation of hydrograph assumes pandas objects, but with 2.0 we have (silently?) moved to having xarray as the default data object.

Suggested implementation: check object type and convert internally to pandas is the easiest. Rewrite entirely to xarray might be better.

[BSchilperoort]

we have (silently?) moved to having xarray as the default data object.

This makes sense with output from distributed models (e.g. PCRGlobWB), as they provide discharge for every pixel.

Suggested implementation: check object type and convert internally to pandas is the easiest

I think that's fine. Although be aware that the output should be for only 1 location (i.e. only a single lat/lon coordinate).

Rewrite entirely to xarray might be better.

We should technically keep supporting the pandas input. The function is also so simple that it doesn't matter too much.