this is ticket: #49 We need to only select a geographical region from the ccm plus all downstream segments within this region.
Below we use the ST_Contains function

/*boolean ST_Contains(geometry geomA, geometry geomB);
Description
Geometry A contains Geometry B 
*/


-- first trial..
/*
SELECT count (*) from ccm21.riversegments r
join (SELECT ST_Union(f.the_geom) as singlegeom
    FROM france.departement As f) as sub
ON ST_Contains(sub.singlegeom,r.the_geom); 
*/
 -- we try to get the vector of seaoutlets that are within the geographical area
select * from ccm21.riversegments r where wso_id in (
select distinct on (wso_id)  wso_id from ccm21.riversegments r
join (SELECT ST_Union(f.the_geom) as singlegeom
    FROM france.departement As f) as sub
ON ST_Contains(sub.singlegeom,r.the_geom)); --170703 lines