Nature, food, and water 257walkway (Color Figure43)(Binford and Karty 2006, Decamps and Decamps 2001,
Forman 2004a). They provide multiple goals for people and nature, including
connectivity for movement by both aquatic organisms and terrestrial species
along a valley. To be most effective the natural-vegetation ribbon covers the
floodplain, both hill-slopes, and adjacent strips of well-drained upland. Some
high-quality streams (e.g., Riera Sorreigs northwest of Vic) are presently protected
forpart of their length by a stream corridor. Four major issues are addressed:
(1) water quality; (2) floodplain riparian vegetation; (3) industries, streams, and
rivers; and (4) four rivers.
Wat er quality
Fourtypes ofwatermay be recognized: (1) looks and is dirty; (2) looks
clean but isn’t (it’s not safe for swimming or eating fish); (3) swimmable and
fishable (it’s safe to swim and eat the fish, but don’t drink a drop); and (4) drink-
able (potable). An aquatic biologist can easily describe these types rigorously
from the aquatic life present (Rieradevall and Cambra1994,Pratet al.2002).
Almost all the streams and rivers in the Greater Barcelona Region have the first
type of water; they mostly look and are dirty. They are unswimmable, unfish-
able, and undrinkable. At present, drinkable water basically comes from wells
in uncontaminated groundwater or from surfacewater that goes through an
expensive water-treatment facility.
Mineral nutrients, with nitrogen and phosphorus of prime concern in the
region, are introduced into streams and rivers in human sewage, livestock (par-
ticularly pig) waste, and greenhouse fertilizer use (Color Figure43). Nitrate
levels are so high in groundwater north of Vic that the public water supply
is apparently unsafe to drink in 20 to 30 towns. (A few towns near the Tordera
River seem to have the same problem). Both surface runoff and groundwater
flows carry nitrogen and phosphorus to the Ter River and its tributaries, which
thereby become eutrophicated (filled with green floating algae because of the
enrichment). The river then carries the nutrients, which eutrophicate the all-
important reservoirs. Sodium and chloride from salt mines and mine-waste piles
in the Cardona and Navas valleys reduce water quality somewhat down the entire
Llobregat to its mouth. Also, industrial pollutants are probably a widespread
water problem in the region.
Floodplain riparian vegetation
Typically 80 to 95 % of the water entering a stream system enters in
thesmall upper tributaries, whereas flood hazard is primarily in the lower por-
tion. Water that enters the upper channels is either absorbed into the ground
to recharge the surrounding groundwater, or it rushes downstream.Riparian