Journal of Water Resource and Protection, 2013, 5, 723-731
http://dx.doi.org/10.4236/jwarp.2013.57073 Published Online July 2013 (http://www.scirp.org/journal/jwarp)
Constructed Ponds and Small Stream Habitats:
Hypothesized Interactions and Methods to
Minimize Impacts
Jonathan D. Ebel1,2, Winsor H. Lowe1
1Division of Biological Sciences, University of Montana, Missoula, USA
2Biology Department, Memorial University of Newfoundland, St. John’s, Canada
Received April 28, 2013; revised May 29, 2013; accepted June 21, 2013
Copyright © 2013 Jonathan D. Ebel, Winsor H. Lowe. This is an open access article distributed under the Creative Commons Attri-
bution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
ABSTRACT
Extensive research has been conducted on how large impoundments and reservoirs affect hydrologic, geomorphologic
and ecological processes in downstream ecosystems. Surprisingly, few studies have addressed the effects of smaller
impoundments and constructed ponds. Pond construction has been considered an important tool for managers seeking to
reduce sediment, nutrient and pollutant loads, and increase habitat heterogeneity in streams in an effort to conserve or
enhance aquatic species diversity. However, we lack information on the interaction between ponds and stream habitats,
which may compromise the efficacy of conservation efforts. The objective of this review is to outline possible physical
and biological changes to stream ecosystems resulting from pond construction. Greater understanding of how ponds
influence watershed processes at various spatial scales is crucial to evaluating the effects of constructed ponds on
stream ecosystems.
Keywords: Headwater Streams; Discharge; Nutrient Retention; Spatial Scale; Lotic; Lentic
1. Introduction
Research on the effects of large impoundments on down-
stream ecosystems has largely focused on reservoirs and
rivers. Numerous studies have shown that impoundments
cause drastic changes in ecosystem structure throughout
watersheds and even continents by changing numerous
ecological, hydrologic, and geomorphic processes [1,2].
At smaller scales, stream ecologists have long been in-
terested in the effect of wetlands and beaver impound-
ments on stream fishes, aquatic macroinvertebrates, wa-
ter chemistry and geomorphic characteristics [3,4]. Lake-
stream interactions have been recently reviewed in an
attempt to guide future research on incorporating lakes
into the river continuum [5]. However, little research has
addressed the interaction of human-constructed ponds
and adjacent streams, despite the global proliferation of
small impoundments and diversions and an increase in
the number and geographic extent of anthropogenic ponds
[2].
Ponds number in the millions worldwide [2]. At the
continental scale, ponds may play a measurable role in
the global carbon cycle [6] and sediment movement [2].
At regional and watershed scales, ponds can reduce
stream sediment loads and nutrient concentrations [7]. It
is well documented that pond construction can benefit
regional biodiversity by increasing freshwater habitat
heterogeneity [8]. Furthermore, ponds can support a
range of recreational activities for humans, be used to
improve water quality, and provide other important eco-
system services. Overall, the construction of ponds with-
in highly degraded or biologically depauperate water-
sheds can be a beneficial prescription. Yet, we know lit-
tle of how ponds alter stream ecosystem dynamics, espe-
cially in relatively undisturbed watersheds.
Despite the recent proliferation of artificial ponds
within watersheds throughout the United States, there is
limited literature examining the effect of these ponds on
in-stream habitat. The current lack of understanding of
pond-stream interactions underscores the need to provide
a synthetic framework to guide future research and man-
agement of watersheds with respect to the construction,
placement, and maintenance of constructed ponds. In this
synthesis, we provide a broad examination of the effects
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J. D. EBEL, W. H. LOWE 724
of constructed ponds on in-stream habitat. We focus this
discussion on hypothesized alteration of physical and
biotic processes in adjacent streams because stream habi-
tat is formed, maintained, and altered by the reciprocal
interactions of these processes. This review is purposely
interdisciplinary because of the inherent complexity of
the topic. Our primary goal is to step back from the de-
tails of in-pond dynamics in order to call attention to
broader patterns of pond-stream interactions and to iden-
tify specific points of relevance to conservation and ma-
nagement.
Streams integrate landscape properties in a hierarchi-
cal fashion, moving from network, to stream, to reach, to
habitat [9,10]. Our vision of the interaction of ponds and
streams applies hierarchical patch dynamic [11] and
network dynamic [12] perspectives of the river contin-
uum. Specifically, we suggest that the effect of construc-
ted ponds on streams depends heavily on pond density at
the network scale and individual pond design at the
stream, and habitat scales (Figure 1). While pon d design
is designated by landowners and tends to lie within the
confines of regio na l and f ederal r egu latio ns, pond den sity
within a stream network depends on the dominant land
use and the aggregative (and possible cumulative) actions
of many landowners.
2. Terminology
Constructed ponds are highly diverse with respect to
their purpose, design, water storage capacity, catchment
characteristics (i.e., surrounding land use, vegetation)
and biota. As a result of this diversity, ponds are difficult
to define. We define constructed ponds as man-made
Figure 1. Multiple scales of physical and chemical conse-
quences of constructing on-stream (hatched) and off-stream
(black) ponds for small stream habitats.
water bodies with areas between 10 m2 and 60,000 m2
that hold water throughout the year. To further restrict
the types of waterbodies discussed here, we will fo cus on
those ponds that gain water through the direct impound-
ment or diversion of surface flow, rather than solely
rainfall and/or groundwater. Diversion-fed ponds are
often built by landowners and government agencies to
serve a variety of purposes, including water supply for
livestock, sediment trapping, erosion control, nutrient
removal, recreation, and aesthetic improvement [13].
In this context, we can place constructed ponds in one
of two categories; 1) on-stream ponds-built by impound-
ing the existing stream channel and causing an abrupt
shift from lotic to lentic habitat where the stream enters
the pond and fro m lentic to lotic at the impound ment, and
2) off-stream ponds, which require the diversion of part
of total stream discharge and are located in the f loodplain
adjacent to the stream channel (Figure 1).
On-stream ponds can be viewed as a single patch
within a stream network, as conceptualized by hierarchi-
cal patch dynamic perspective of the river continuum
[11]. According to this perspective, a stream is com-
prised of hierarchically nested patches arranged longitu-
dinally in space. Patches have unique community and
biogeochemical structures and functions that vary with
time, although the dynamics of individual patches are not
independent of other patches. Therefore, biological and
chemical fluctuations within an upstream patch can alter
the dynamics of downstream patches.
Off-stream ponds alter stream network structure by
removing flow at the point of diversion, much like a
braided channel, and creating a confluence at the point
where the effluent discharge channel joins the stream.
Here, we apply a network dynamics perspective because
braids and confluences can cause locally abrupt changes
in water chemistry and sediment flux while also altering
channel and floodplain characteristics [12]. At the net-
work scale, the number and arrangement of off-stream
ponds interact with the natural stream to influence the
diversity of stream habitat patches by the accumulation
of local changes to biogeochemical and geomorphologi-
cal characteristics.
3. Alterations of Physical Conditions
3.1. Flow Regime
The residence time and amount of water in ponds may
reduce temporal variation in stream discharge, mimick-
ing the flow regimes downstream of mountain lakes and
beaver ponds. Residenc e time is calculated as the volume
of the pond divided by inflow per unit time. In snowmelt
dominated lake-stream systems, the retention of water in
a lake reduces the magnitude and increases the duration
of over-bank flooding events downstream [14]. The

J. D. EBEL, W. H. LOWE 725
downstream flow regime is dictated by the water level in
the lake. Beaver ponds also dampen peak flows and in-
crease low flows [15]. Despite the highly variable outlet
structures of on-stream ponds, water level relative to out-
let elevation remains the dominant control of discharge.
Off-stream ponds should have more variable effects on
flow regimes, mainly the magnitude and duration peak
flows. We predict the degree to which off-stream ponds
alter flow regimes to be a function of the percentage of
flow diverted into the pond and the ratio of undiverted
flow to effluent discharge.
At the watershed scale, the ratio of constructed pond/
wetland area to total watershed area is one of the most
important factors determining the capacity of a watershed
to decelerate high stream flows [16]. At the scale of indi-
vidual ponds and the adjacent stream, deceleration of
flow and sediment trapping capacity depends on resi-
dence time of the pond. Variation in residence times
among ponds of similar volume and inflow rate is par-
tially attributed to differences in hydraulic efficiency,
defined as the efficiency with which the volume of the
pond is utilized [17 ]. Features that improve the hydraulic
efficiency of constructed ponds include an elongated
shape, submerged terraces, baffles and islets [17]; all of
which act to distribute the energy of inflowing water
throughout the pond and minimize sediment re-suspen-
sion events during high flows [18]. With respect to sus-
pended sediments, higher residence times in the pond
allows more suspended sediments to settle out o f the wa-
ter column. Pond designs with long residence times cou-
pled with high hydraulic efficiencies should have the
largest effect on natural flow regimes and sediment loads,
with consequences for substrate characteristics and habi-
tat complexity in receiving streams.
3.2. Sediment Load and Habitat Complexity
By decelerating flow and allowing suspended particles to
settle out of the water column, ponds reduce the load of
fine sediments downstream by acting as a sediment sink.
Discontinuity of sediment loads due to lentic habitat
patches can have profound effects on physical attributes
of downstream segments. For example, a study charac-
terizing the influence of glacial lakes on the physical
form and function of mountain streams in central Idaho,
USA, found that sediment size, channel shape, and sedi-
ment entrainment is best described by the location of
sediment sources (e.g., hillslopes and tributaries) and
sinks (e.g., lakes) because fine sediments are removed
and downstream flow regime is altered [19]. Because
elevated sediment loads in streams often have negative
effects on stream organisms [20], ponds have been pre-
scribed as a conservation tool to lower suspended sedi-
ment concentrations in watersheds disturbed by agricul-
tural development, ro ad construc t ion, or fi res [18].
In relatively undisturbed streams, the relationship be-
tween suspended sediment load and discharge is viewed
as a dynamic equilibrium that can be disrupted by
changes in either sediment load or discharge [21]. Con-
structed ponds can alter the suspended-sediment dis-
charge relationship by 1) changing the discharge regime
by diverting flow and increasing water residence time at
the pond location, 2) changing channel morphology by
building impoundments, diversion and effluent channels,
and the pond itself, and 3) slowing the downstream
transport of bed load materials and suspended sediment
from sources upstream in the watershed.
While used as a measure of success for restoration
projects in many disturbed watersheds, drastically low-
ered sediment loads in undisturbed watersheds disrupt
the relationship between the load and size of sediments
(i.e., supply) and stream power—a function of stream-
flow discharge, water surface slope, and the specific
weight of water. Channel degradation, or the localized
removal of channel bed material by stream water without
adequate deposition, occurs when stream power exceeds
the sediment supply [21], and can lead to channel inci-
sion and streambed armoring [28]. The magnitude and
extent of channel degradation depends heavily on the
location of new sources of sediment downstream. Chan-
nel incision below off-stream ponds can be easily
avoided by constructing a low gradient effluent channel
with low water surface slope.
Streambed armoring occurs when only small particles
are entrained and the resulting streambed consists of
large substrates that are immob ile during bank-full flows
[19]. We predict that armoring below on-stream ponds
and some off-stream ponds is more likely to occur than
channel incision because it is more difficult for land-
owners to maintain the supply of small sediments to the
downstream streambed at pre-pond levels. In most cases,
small sediment supply will be negligible immediately
below on-stream ponds and greatly reduced below off-
stream ponds with high ratios of diverted stream dis-
charge to un-diverted stream discharge and effluent dis-
charge to receiving stream discharge.
3.3. Temperature
The direct discharge of high temperature water from a
pond into a stream can increase temperatures of the re-
ceiving stream to above normal levels [22]. Excellent
literature reviews exist that explore th e fundamental con-
trols on stream water temperature [23] and biological
responses to temperature variation [24]. We suggest four
important factors that interact to influence in-pond water
temperatures and consequent effects of effluent discharge
on the temperature regimes of receiving streams: 1) the
placement of a pond within a watershed, 2) the surface
area to volume ratio of the pond, 3) light penetration in to

J. D. EBEL, W. H. LOWE 726
the pond, and (4) residence time of stream water in the
pond.
Pond surface area to volume ratio (SA:V) governs the
efficiency of radiant heating and water column mixing
[25] because the exposure of a pond to radiant energy
and wind increases with surface area. Pond depth influ-
ences light penetration and whether wind mixing will
affect the hypolimnion. Differences in light penetration
among ponds leads to variation in radiant heating of
ponds with similar SA:V. Light penetration is influenced
primarily by aquatic macrophyte coverage and pollution
[26]. The heated water is then discharged from the pond
back into a stream, altering downstream temperatures
during summer months when low flows and high tem-
peratures already may cause harm at a critical time in the
life histories of stream organisms [27].
In general, ponds fed by headwater streams tend to be
much cooler than ponds fed by larger streams in the same
system [28]. Because ponds have a greater thermal iner-
tia than small streams, warmer water temperatures may
persist in ponds into the autumn months. The steepest
temperature gradients in a stream-pond network occur at
pond-stream transitions, and the gradient between up-
stream and downstream temperature is steeper for on-
stream ponds as opposed to off-stream ponds. An exam-
ple of the former is described by Maxted et al. [22], who
observed higher mean daily stream temperatures th-
roughout the summer and autumn in streams below on-
stream ponds in New Zealand, especially below ponds
lacking riparian canopy cover. Similarly, Jones and Hunt
[29] found that off-stream ponds acted as point sources
of thermal pollution. In some ponds, however, substantial
input of stable temperature groundwater can reduce diel
temperature ranges and keep ponds cooler than the adja-
cent stream regardless of a ponds lo cation in a watershed
(Ebel and Lowe, unpublished data).
Changes in water temperature have consequences for
the lotic communities and ecosystem processes by limit-
ing dissolved oxygen concentrations, influencing the
feeding and metabolic rates of stream organisms and al-
tering microbially mediated nutrient cycling [30]. In
streams dominated by species that require low, stable
water temperatures, like many in the Northern Rocky
Mountains, water temperatures exceeding 20˚C lead to
decreased growth rates and survival of salmonids [31].
On-stream ponds will likely cause an abrupt change in
temperature and biotic community structure [1] along a
longitudinal gradient encompassing the pond and adja-
cent upstream and downstream reaches. The direction of
the temperature gradient depends on whether pond ef-
fluent is released from the surface (warmer effluent) or
from the bottom of the pond (colder effluent). The effect
of off-stream ponds with regulated headgates [32] will
likely be less than on-stream ponds, and should vary
seasonally depending on the amount of inflow, residence
time of water in the pond, and the ratio of effluent flow
and temperature to mainstem flow and temperature [33].
We hypothesize that discharge from off-stream ponds
affects stream temperatures more when those ponds are
located along lower-order headwater streams with lower
flows and higher pond -to-stream temperature ratios.
The most effective strategy to prevent artificial in-
creases in stream temperature from pond effluent is to
prevent pond temperatures from reaching levels beyond
the tolerances of native stream organisms. This can be
accomplished by designing ponds with low surface area
to volume ratios, altering outlet structures such that ef-
fluent is drawn from the lower strata of the pond, or
minimizing the ratio of effluent discharge to receiving
stream discharge.
4. Alteration of Chemical Conditions
The creation of standing water along a stream changes
the downstream transport of nutrients. For this reason,
pond construction is a common technique used by envi-
ronmental engineers and stream restoration practitioners
[7]. Summarizing the nutrient chemistry of ponds is
made difficult by the range of pond designs, the varying
sources of nutrients from the atmosphere and watershed,
intricacies of nitrogen and phosphorous dynamics within
ponds, and widely differing water retention times. The
details of these processes have been extensively reviewed
elsewhere [34]. It is well understood that ponds can im-
prove the water quality of streams degraded by intensive
mining and sewage treatment plant effluent; however,
changes to the chemical cycling of currently unimpacted
streams may alter microbially mediated chemical cycling
with unintended consequences for intact lotic food webs
and must be considered during watershed planning.
Overall, the degree to which a constructed pond will in-
fluence streamwater chemistry is design and region de-
pendent, requiring pond architects to have in-depth
knowledge of watershed characteristics if in-stream ef-
fects are to be minimized.
Phosphorous (P) sorption and desorption in aquatic
systems are governed by the structure of sediment parti-
cles, the degree of phosphate saturation, and sensitivity
to environmental changes [35]. Pond sediments can be a
temporary phosphorous sink and provide an important
ecosystem service, especially in agricultural areas, by
reducing phosphate concentrations downstream. A
Swedish study estimated that a constructed, open water
wetland retained 17% of mean annual P load over 4 years,
with 78% of retained P held in sediments close to the
inlet [36]. Retained P in this wetland was predominately
in potentially mobile forms; i.e., organic P and P associ-
ated with iron or aluminum. Potentially mobile implies
that P can be released from sediments. P-release from

J. D. EBEL, W. H. LOWE 727
sediments into pond effluent depends on the sediment
phosphate capacity and varies seasonally because warm-
ing water temperatures can promote phosphate release by
the increasingly anoxic conditions at the sediment-water
interface associated with increased microbial activity
[37]. Released phosphates can be exported to adjacent
streams through pond efflu ent. Such pulses of pho sph ates
can be especially harmful to headwater systems where
phosphate concentrations will depend mainly on effluent
discharges since background concentrations are close to
detection limits [35 ]
In headwater streams, the majority of energy driving
the system is derived from allochthonous sources [28].
Impoundments greatly depress the ratio of course par-
ticulate organic matter to fine particulate organic matter
as the downstream movement of detritus is blocked and
phytoplankton and fine sediments is discharged from the
pond. Nutrient loading of ponds and nutrient discharges
can stimulate in situ production by in-pond phytoplank-
ton communities and in-stream biof ilms possibly altering
the trophic state of the recipient stream [38]. Discharge
of pond autotroph biomass (either dead or alive) can
change the energy dynamics of downstream co mmunities
by shifting the predominant source of utilizable carbon
from recalcitrant leaf litter to labile algal photosynthates.
This shift in major energy source would cause changes in
downstream macroinvertebrate community assemblage
and production.
Well placed, designed, and managed ponds can play a
critical role in the removal of nitrogen from streamwater,
but can discharge retained nitrogen under some condi-
tions. Pond construction can stimulate nitrogen removal
by providing the anaerobic conditions necessary for de-
nitrification pathways. Total nitrogen removal often var-
ies between 40% and 55% of total input depending on
the design of th e pond or wetland and nitrate lo ading rate.
Nitrate not removed through denitrification is trans-
formed and retained by burial and sorption to sediments
and is thus available to be discharged during high flow
events, pond dredging, or outflow control failures. Such
nitrogen pulses can cause changes in downstream biotic
communities. For example, Selong and Helfrich [39]
found that overall macroinvertebrate species richness
decreased below constructed trout ponds. The reduction
in overall species richness was accompanied by a de-
crease in the ratio of mayflies, stoneflies, and caddisflies
to chironomids, and the ratio of shredders to the total
insects. They attributed the shift in the macroinvertebrate
community to increased nitrogen levels caused by high
concentrations of nutrients in off-stream pond effluent
during pond-dredging events and pond nutrient enrich-
ment by trout feeding loads.
5. Biotic Changes
Research on ponds and biodiversity is r apidly increasing,
showing that ponds increase regional biodiversity and
promote rare aquatic species [40]. Specific management
techniques to maximize pond biodiversity have been re-
viewed [8]. The arrangement and size of constructed
ponds within a watershed can in fluence the effectiveness
of pond construction as a tool for biodiversity conserva-
tion. For example, Oertli et al. [41] found that many
small ponds in close proximity to each other can support
greater regional biodiversity than a few large ponds.
Furthermore, the creation of areas of high pond density
that provide increased habitat complexity and maintains
high among-pond connectivity can help to sustain per-
sistent metapopulations of rare species [41]. However,
the benefits of pond construction aimed at protecting rare
lentic species should be weighed against the possible
costs of de-stabilizing intact stream ecosystems.
Habitat alterations and subsequent biological invasions
are cited as two major drivers of biodiversity loss world-
wide. Clearly, the excavation of a pond causes a drastic
change in the local biotic community on the floodplain
by creating lentic habitat where it did not previously exist.
Increases in invader abundance typically follow any
natural or anthropogenic disturbance [42] and the dis-
turbed floodplains and streams provide a prime opportu-
nity for invader establishment. In addition to the suscep-
tibility of newly-constructed ponds to biological inva-
sions, constructed ponds also can pose a threat to native
species assemblages in adjacent streams by decreasing
the ability of stream communities to resist invasions.
An invader of increasing importance to the health of
streams in the western USA is Myxobolis cerebralis, an
invasive myxosporean parasite identified as the cause of
whirling disease in salmonid species. Allen and Ber-
gersen [43] found the high est densities of Tub ifex tubifex,
the invertebrate host of M. cerebralis, in the Poudre
Rearing Unit (PRU) of the Cache la Poudre River in
Colorado, a trout rearing facility consisting of a series of
off-stream ponds. T. tubifex densities were three orders
of magnitude higher in the PRU than in all alcoves and
eddies along the stream reach. Similar results were found
on the Salt River, Wyoming [44], and the Fryingpan
River, Colorado [45], where ponds served as point
sources of infectious triactinomyxons (spore emitted into
the water column by the invertebrate host; TAMs).
Measures of juvenile rainbow trout infection and re-
cruitment rates, as well as densities of infected T. tubifex,
indicate that the complete infection of all salmonids in a
system requires very few T. tubifex and TAMs. Out-
breaks of whirling disease greatly reduce salmonid re-
cruitment in cold, oligotrophic, sediment poor, high gra-
dient streams [43], especially during times of decreased
stream flow [46]. Several techniques have been used to
decrease the concentrations of TAMs in pond effluent,
the most efficient being sand filtration [45]. As a severe

J. D. EBEL, W. H. LOWE 728
threat to wild salmonid populations across the western
United States, more information is needed on the role of
on- and off-stream ponds in the spread and severity of
whirling disease outbreaks.
Increases in physical heterogeneity of stream systems
can cause variation in colonization, persistance and dis-
persal of both vertebrates and invertebrates. For example,
Schlosser [4] concluded that discharge-mediated interac-
tions between beaver ponds and streams benefited creek
chub populations (Semotilus atromaculatus) by control-
ling fish dispersal, fish diversity, fish predation, and mac-
roinvertebrate community composition (e.g., densities in
riffles vs. pools during high and low discharge). Knutson
et al. [47] came to a similar conclusion, relating the per-
sistence of amphibian populations to the increase in
breeding habitat as a result of pond construction. In con-
trast, Olsson et al. [48] found that the physical habitat
alteration associated with constructed ponds caused in-
creased mortality of migrating brown trout smolts (Salmo
trutta) in Sweden. They attributed this increase in smolt
mortality to the shift to standing water habitat, causing
changes in downstream migration speed and exposing
smolts to increased levels of predation. In this case, an-
thropog enic changes to th e physical heterogenity of streams
had a negative effect on recruitment because the specific
population of brown trout had not evolved to survive in
standing water habitats.
6. Conclusions and Future Challenges
Constructed ponds have situation-specific effects on ad-
jacent streams; a single pond may alter physiochemical
and biotic conditions at scales ranging from local habitats
to entire stream segments. In lower order drainages with
high pond density, the cumulative effects of on and/or
off-stream ponds may alter entire watersheds. Decisions
on whether to construct ponds along streams and how to
manage existing ponds must be evaluated based on the
broader goals of human communities within the water-
shed, as well as management and conservation objectives
of local, state, and federal governmental entities. There is
a mismatch between the proliferation of constructed
ponds and the current state of empirical knowledge re-
garding the myriad of possible consequences for stream
ecosystems. Small-scale and short-term studies are in-
adequate because they fail to accurately identify threats
and critical scales of management [49].
Pond construction and management must delicately
balance recreational and economic needs while minimiz-
ing alterations or disturbances to adjacent stream ecosys-
tems. Before effective policy for pond construction can
be implemented, it is imperative that we answer the fol-
lowing questions:
1) What types of streams and geographical regions are
most susceptible to the negative effects of constructed
ponds?
2) Can pond design and management protocols over-
come negative effects on sensitive streams or regions?
What designs and protocols are most effective?
3) How many ponds along a stream are necessary to
achieve restoration or mitigation goals while minimizing
negative or cumulative effects on in-stream habitats?
Although the design and placement of a pond is wa-
tershed-specific, a well-designed pond should achieve
two objectives: 1) increase the biodiversity of a water-
shed by providing increased aquatic and riparian habitat
complexity and valuable ecological services (e.g., sedi-
ment trapping, nutrient retention) and 2) minimize nega-
tive effects on natural stream processes and habitat.
Many questions about pond-stream interactions remain
unanswered, illustrating our limited understanding of in-
teractions among aquatic ecosystems and how these in-
teractions should influence management decisions. Al-
though some researchers suggest that the construction of
ponds should be encouraged because they can facilitate
the persistence of rare aquatic species and increase the
biodiversity of a watershed [8], pond construction can
also pose serious threats to the overall ecological health
of a watershed. Processes resulting from the interaction
of constructed ponds and nearby streams are varied and
complex. Our understanding of these interactions would
benefit from quantification of downstream changes in the
physical, chemical and biological variables discussed in
this review in a Before-After-Control-Impact study fra-
mework [50] Furthermore, the recognition that material
processing within pond and stream habitats is spatially
dependent will provide the means to place constructed
ponds in the context of entire landscapes [51]. The con-
nection of ecological processes of constructed ponds to
stream habitats is essential to pond management p ractices
that maintain the biological integrity of watersheds.
7. Acknowledgements
This review was supported by funding from the Rock
Creek Trust and Five Valley Land Trust, Missoula, MT,
Montana NSF EPSCoR, and the Howard Hughes Medi-
cal Institute through the MILES program.
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