environmental
canal
catchment
concrete
conduit
culvert
dirty
drain
drainage
drainpipe
duct
dump
environment
flood
floodwater
flow
forest
green
industrial
industry
large
moss
opening
outfall
outflow
outlet
overflow
pipe
piping
pollution
pouring
rain
rainwater
run off
runoff
sanitary
sewage
sewer
sewerage
spout
storm
stormwater
stream
summer
system
tube
two
waste
wastewater
water