The D env e r Basi n Ru l e s
Areas along the South Platte River contain not-nontributary groundwater. In 1985, complex legislation commonly known
overlying streams, and were actually not
Senate Bill 5 required that the Denver
as Senate Bill 5 took into consideration the rec-
non-tributary. Unfortunately, the confus-
Basin aquifers be evaluated for their po-
ommendations of the “blue ribbon” committee.
ing wording “not-nontributary” stuck dur-
tential hydraulic connection to surface
Specific statutory language and definitions were
ing the rule-making process and is still
water. This was accomplished by the
developed to address the allocation of the Denver
used today.
State Engineer’s Office through model-
Basin and Dakota aquifers, as well as all other
Not-nontributary groundwater refers
ing. To avoid having to evaluate how to
non-tributary groundwater statewide. Senate
to those parts of the Denver Basin aqui-
replace this water on a case-by-case ba-
Bill 5 also required the State Engineer to
fers which are in some way connected to
sis, a blanket strategy for replacing water
promulgate rules and regulations govern-
surface streams or the aquifers where they
potentially removed from local rivers by
ing the withdrawal of groundwater from
outcrop. Examples that contain not-non-
well pumping was implemented. The leg-
the Denver Basin aquifers by December
tributary groundwater are areas along the
islation required judicial approval of plans
31, 1985. These became know as The Den-
South Platte River or the various streams
for augmentation at different standards
ver Basin Rules. While this legislation did
within the basin such as Monument Creek,
of four percent of withdrawals or actual
not specify how groundwater in the basin
Plum Creek and Cherry Creek.
depletions depending upon the aquifer
should be managed over the long-term,
For parts of the Denver Basin not within
and the distance from the stream contact.
it did provide a basic legal framework for
a designated basin, the water court has ju-
These replacement requirements do not
how the groundwater of the Denver Basin
risdiction to enter decrees for the use of
apply to groundwater within the desig-
should be allocated.
water. In the designated parts of the Den-
nated basins.
By enacting this legislation, the Gen-
ver Basin, the 1/100th per year pumping
eral Assembly agreed that it was accept-
rule applies and the Ground Water Com-
Municipal Rights to
able to mine the Denver Basin aquifers
mission makes all determinations regard-
Denver Basin Groundwater
by taking out more water than was being
ing the allocation and use of water.
As development of the Denver Basin aquifers progressed, cities and water districts
replaced. This was allowable even though reduction in the artesian head or water
Replacing Depletions from Streams
wondered what rights they have to develop
levels in the aquifers would occur, and
Though the General Assembly defined
groundwater beneath their communities.
some wells might be impaired.
non-tributary groundwater as not con-
Initially, water was allocated to the
The legislature also clarified that non-
nected to surface water, they realized
overlying landowner at the rate of one
tributary groundwater is “water which in
some hydrologic connection may be evi-
percent of the aquifer resource per year.
100 years will not deplete the flow of a
denced over very long timeframes. Con-
Landowner consent is normally required
natural stream at an annual rate greater
sequently, Senate Bill 5 provided that not
to extract Denver bedrock water from un-
than 1/10th of one percent of the annual
all the water withdrawn from the non-trib-
der a person’s property.
depletion from the well.” This definition
utary Denver Basin aquifers could be con-
SB 5 clarified that municipalities and
applies primarily to the Denver, Arapahoe
sumed; two percent had to be replaced.
water districts by implied consent may
and Laramie-Fox Hills aquifers.
The State Engineer generally assumes
utilize the Denver Basin groundwater re-
that this provision is met by return flows
sources within their boundaries, if they
from outdoor watering or other sources.
provide a reasonable alternative water
The legislature also recognized that some of the deep Denver Basin aquifers were not completely dissociated from
The not-nontributary designation in
supply to the land owners.
Citizen’s Guide to Denver Basin Groundwater
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