Phosphorus sources and transport in the Upper Waitaki catchment
By Duncan Gray, Adrian Meredith and Graeme Clark
Introduction
Phosphorus and nitrogen are the primary nutrients required for the growth of plants. However, an
excess of phosphorus in streams, rivers and lakes can result in the occurrence of nuisance growths of
algae and plants, which may degrade ecological, cultural, aesthetic and recreational values. This
memorandum explores the pathways to and cycling of phosphorus in waterways. We also present
the results of an estimation of the phosphorus reference condition in the upper Waitaki catchment
and compare these values to measured phosphorus in streams.
Phosphorus (P) within waterways and downstream lakes takes four primary forms; dissolved or
particle bound, and organic and inorganic. These forms vary in their pathways to the river, cycling
characteristics, concentrations, and bioavailability (Withers & Jarvie 2008). Inputs may be episodic if
driven by flood / erosion events or discrete discharges, or more regular if associated with continuous
discharges, internal cycling, base flow or groundwater. The relative proportions of the different
phosphorus (P) forms which contribute to the total phosphorus load vary widely between catchments
and over time (Withers & Jarvie 2008).
Pathways to streams
Natural, or background, sources of P include natural weathering of soil parent materials, atmospheric
transport of dusts and organic materials (Holtan et al. 1988), decomposition of in-river and riparian
vegetation (Meyer & Likens 1979), river bank erosion (Walling et al 2008), leaching of water through
soils, and losses from animals, fish and birds (Nislow et al. 2004; Clarke and Meredith 2014). In general,
natural loads are very low as phosphorus is not abundant in the majority of New Zealand geologies,
with the exception of limestone, mudstone, and some igneous rocks (Mainstone & Parr 2002).
The immediately bio-available dissolved inorganic form of phosphorus (dissolved reactive phosphorus
(DRP) or soluble reactive phosphorus (SRP)) enters streams in small quantities leached through soils
and in groundwater, or in land surface run-off. The contribution of the groundwater pathway is highly
dependent on the properties of soils through which percolating water must pass. Heavy clay soils
provide a high adsorption capacity for P, whereas sandy or gravely soils or with underlying sandstone
geology have a low P retentive capacity (Mainstone & Parr 2002). Soils with preferential flow paths
(cracking and discontinuities), thin shallow soils, and soils with a high ground water table, all have
increased potential for P leaching to groundwater and streams. Anoxic soils (those with low dissolved
oxygen and/or low pH) can also inhibit phosphorus retention onto soil particles and lead to increased
leaching.
Dissolved organic forms typically reach streams through soils, particularly anaerobic wetland soils, and
groundwater as well as surface runoff (Parfitt et al 2013). This soluble form requires microbial
processing prior to uptake by plants.
The majority of phosphorus load is likely to be within organic particles or primarily as particle bound
inorganic phosphorus, particularly in streams draining steep erodible hill country. During storm
events, slips and bank erosion may contribute large quantities of sediment and hence phosphorus
load to streams. This phosphorus is not immediately available to algae which predominantly derive
nutrients from the water column, but constitutes a reservoir of phosphorus if deposited in the stream
bed. Rooted macrophytes (plants) predominantly access phosphorus via their roots from bed
sediments. Steep, flashy streams tend to flush sediments and associated phosphorus downstream.
However, stream reaches which are slower flowing or have depositional areas, such as a floodplain,
may accumulate sediment and phosphorus following flood events. This phosphorus may provide a
slow release source to the stream during low flow periods.
Internal cycling
Phosphorus budgets for streams often show that the phosphorus load estimated to enter streams
from a catchment may be greater than the amount measured in water concentrations leaving a
catchment. This is because streams, particularly during stable flows, retain phosphorus through
biogeochemical cycling processes and storage. However, at high flows substantial loads of phosphorus
may be exported. Given the typically low dissolved phosphorus concentrations derived from
catchment geology, a significant proportion of the dissolved plant available phosphorus (dissolved
reactive phosphorus; DRP) measured in streams at low flow is derived from internal cycling of P from
the deposited particulate load (Withers & Jarvie 2008). Once in a river phosphorus is highly chemically
and biologically active, undergoing numerous transformations and moving between the particulate
and dissolved phases, between the sediment and water column, and between biological and inorganic
forms (Mainstone & Parr 2002). Phosphorus in sediment can desorb rapidly into the water column as
DRP when the relative concentrations of phosphorus in the sediment is high (Mainstone & Parr 2002).
This equilibrium mechanism provides a constant supply of plant available phosphorus to the water
column irrespective of DRP inputs to the stream or uptake by algae. At low, stable flows, when plant
and algal uptake is high, stream water concentrations and algal growth may be maintained at constant
and productive levels by diffusion from stream bed sediments.
Particle bound phosphorus may also be incorporated into plant and algal biomass directly from
sediments. Most rooted macrophytes derive phosphorus from stream sediments and are unaffected
by low dissolved phosphorus availability in stream water (Withers & Jarvie 2008). Similarly mat
forming algae will grow over fine sediments and intercept diffusing phosphorus (Dodds 2003). Algal
mats also engineer conditions within the mat which allow the extraction of phosphorus from
entrained particles by biological (enzymatic) or physicochemical (low dissolved oxygen concentration
or high pH) means (Adey et al. 1993). In this way algal species are able to mobilise and access most
components of stored sediment phosphorus. Algal community composition will vary depending upon
the amount of fine sediment accumulated, relative proportions of dissolved or particulate
phosphorus, but also the availability of nitrogen, other trace elements, light and flow (Biggs et al.
2000).
Bacteria and fungi are abundant in algal biofilms and in flowing waters, and contribute to phosphorus
cycling through the breakdown of organic matter, such as detritus, macrophytes and algae, and the
regulation of phosphorus flux between sediments and water (Withers & Jarvie 2008). Although
considered significant, their role in phosphorus dynamics are not well understood or quantified.
Overall, the cycling of phosphorus within a stream provides for a concentration of plant available
phosphorus which is potentially greater than the supply to the stream during low or stable flows.
Much of the phosphorus supply may be delivered in particulate form during storm events, but if
retained within the stream it is then transformed into plant and algae biomass. Accordingly in a natural
stream with low dissolved phosphorus supply the nutrient status is largely determined by the supply
of and retention of phosphorus rich particles within the stream.
This mechanism is illustrated in figure 1. Plot A shows a hypothetical flow regime which features a
period of stable flow followed by a flood event. Plot B shows the supply of phosphorus to a natural
stream in relationship to the flow regime. Particle bound phosphorus supply is very low during base
flow conditions, but shows a sharp increase during rainfall as runoff enters the stream. Dissolved
phosphorus supply to the stream at base flow is also low being derived from soil leaching,
groundwater, and wetlands in the form of dissolved phosphorus. During the high flow and runoff
event there is likely to be a commensurate increase in dissolved phosphorus supply due to increased
leaching rates (McDowell et al. 2001). However, due to dilution there may well be a decrease in the
concentration of dissolved phosphorus as shown in plot C. The residence time of dissolved phosphorus
during high flow events is likely to be short and algal growths are often sloughed and washed
downstream, hence they are not able to use the available phosphorus. Conversely, algal and
macrophyte biomass tends to build up during base flow periods as shown by plot C. A critical point to
note is that the dissolved phosphorus concentration in a stream is likely to be greater at low flow than
would be predicted by supply. This is due primarily to the diffusion of phosphorus into the water
column. The actual concentration will also be dictated by the biomass of algae which is very efficient
at stripping available phosphorus from the water column, and the concentration of phosphorus in
deposited sediments. This situation effectively represents a phosphorus equilibrium pump were
phosphorus stripping from the water column by algae drives an increased gradient between
sediments and water. The dissolved phosphorus concentration may remain relatively constant
assuming an adequate supply is available from bed sediments. The majority of the phosphorus in a
stream is therefore likely to be bound to sediments and not be immediately available, but the
equilibrium pump provides a constant and steady concentration in excess of supply from the
catchment.
Figure 1. Conceptual diagrams showing the relationships between flow, phosphorus supply,
phosphorus concentration and the accumulation of algal biomass.
The conceptual patterns described above are evident in figure 2 which presents actual water quality
data from the Ahuriri River at Diadem. This site is above the majority of agricultural activity in the
catchment and is considered to have relatively natural or un-impacted water quality. Total phosphorus
shows considerable variation presumably associated with high flow events. Dissolved reactive
phosphorus is typically low and shows no consistent response to the concentration of total
phosphorus. It is interesting to note that the concentration of dissolved organic phosphorus is
comparable to that of dissolved reactive phosphorus. Although not immediately available to plants
and algae dissolved organic phosphorus cycles rapidly through stream ecosystems to become plant
available (Withers & Jarvie 2008). Dissolved organic phosphorus is not routinely monitored in streams
and is therefore often an unmeasured and poorly considered component of the dissolved phosphorus
load.
Figure 2. The relationships between dissolved reactive phosphorus, dissolved organic phosphorus and
total phosphorus between Dec. 2011 and Mar. 2013. Data provided by NIWA.
The impact of land use intensification
Land use intensification typically results in an increase in the supply of phosphorus to streams (Allan
& Castillo 2007). Inputs are broadly separated into point source discharges and diffuse discharges.
Point source discharges, e.g. of effluent, emanate from a discrete point and typically remain
relatively constant in volume or discharge rate. Point source discharges may be a significant source
of dissolved phosphorus. Diffuse discharges are often dominated by surface runoff of particulate
phosphorus, but also include phosphorus leached through soils into groundwater. The volume of
discharge corresponds with rainfall events and increased stream flow. Diffuse discharges are most
commonly linked to agricultural sources. Rain or irrigation water mobilises phosphorus along surface
and subsurface flow paths. Sources of phosphorus include soil fertilisers, livestock effluent and
vegetation. The actual proportions of each phosphorus type and source will be highly variable
depending on the rainfall event, land and livestock management, soil and nutrient management
(Withers & Jarvie 2008). Conventional wisdom suggests that the majority of phosphorus lost from
agricultural land occurs as surface runoff of particle bound phosphorus. However, there is
considerable evidence to suggest significant quantities of dissolved phosphorus, both organic and
inorganic can enter streams via surface and sub-surface pathways. This is particularly the case were
intensive animal production results in an excessive phosphorus surplus in soils (Toor et al. 2004). The
problem is exacerbated in coarse textured soils with macropore networks above shallow
groundwater (Webb et al. 2007). The chemistry of animal urine patches can also increase the
transformations and leaching of phosphorus through soils.
The addition of excessive sediment and particulate phosphorus to streams may result in a
biogeochemical time lag which can obscure the response of stream water concentrations to land use
mitigations (Hamilton 2012). Particle bound phosphorus may act as a large exchangeable reservoir
of phosphorus which can enrich water for decades after the supply of phosphorus rich particles to
the stream has stopped. Similarly catchment soils which have become enriched with phosphorus
may provide a source reservoir long after additions to soil have ceased.
Estimating the natural concentration
The phosphorus supply to surface and ground waters in a catchment is determined by a host of factors
which range across spatial scales. Factors such as climate, topography and geology are influential at
large scales. Whereas, soil types, geomorphology and land use practises are important within
catchments and individual reaches of stream (Withers & Jarvie 2008). Concentrations within the
stream are then determined by internal cycling, particularly the retention of sediment bound
phosphorus, biological activity of plants and algae, and physicochemistry of the bed. Thus, nutrient
concentrations in any particular time or place are very difficult to predict. Similarly it is hard to
separate the natural from the anthropogenic loads in any stream. However, recent modelling studies
have attempted to produce reference state water quality predictions for New Zealand Rivers and
streams using the River Environment Classification (REC) (Snelder et al 2004; McDowell et al. 2013).
The REC classifies river reaches according to their source of flow, geology and topography all of which
are pertinent broad scale factors relating to water quality parameters such as total and dissolved
phosphorus.
Estimation of reference conditions must be as accurate as possible to avoid the imposition of trigger
values or expectations that are not achievable, for example due to ‘elevated’ background values. An
accurate estimate of background conditions also aids in the estimation of the ‘anthropogenic’ load
(McDowell et al. 2013). However, it should be noted that any broad scale attempt to estimate
background phosphorus concentrations should be augmented by ‘real’ data where available. Every
stream has its own idiosyncrasies.
McDowell et al. (2013) considered several differing methods to estimate reference conditions. The
simplest method is to use data from a minimally disturbed site that is not subject to present or
historical disturbance. However, such sites are uncommon and may only represent a small subset of
stream types in terms of climate, topography and geology. An alternative approach considered is the
‘historical condition’ that uses available data from before a river became degraded. However, such
data is also typically unavailable. Another option is to look at the range of results from multiple
reference streams within a river type and use a percentile of the distribution as the overall estimate
of reference condition, e.g. the median value for reference upland spring fed streams. A ‘least
disturbed’ condition has also been suggested as a useful guide to reference condition. All of these
options run the risk of setting a reference condition that is too high, due to lack of truly unimpacted
sites.
An alternative approach, preferred by McDowell et al. (2013), is to generate a statistical model using
all the available data; reference as well as impacted. McDowell et al. (2013) produced a model relating
percent heavy pasture in a catchment with median water quality parameters, including total and
dissolved reactive phosphorus (Figure 3). The reference value is assumed to be the point at which the
regression line meets the y axis, i.e. zero percent intensive land use. This method allows a degree of
uncertainty around the reference value to be estimated as a reflection of the strength of the
relationship between water quality and percent heavy pasture. McDowell et al. (2013) also compared
estimated reference values with those measured in sites regarded as minimally disturbed. In order to
assess the anthropogenic influence on water quality McDowell et al. (2013) suggest comparing the
estimated reference values for a site with the median value for each water quality parameter.
Figure 3. An schematic illustration of the McDowell et al. (2013) approach to deriving reference values
for water quality variables in river environment classification (REC) stream types across New Zealand.
Reference phosphorus values in the upper Waitaki
Water quality data for monitored sites in the upper Waitaki zone were compared with estimated
reference median values derived by McDowell et al. (2013). A median value can be basically
interpreted as 50 % of all values being above that number and 50 % below. Streams in the upper
Waitaki catchment vary considerably in terms of climate, topography and geology (Table 1). Different
combinations of these broad variables vary in their estimated reference values for dissolved reactive
and total phosphorus. Not all combinations of stream type found in the catchment had adequate data
to model a reference condition. In particular McDowell et al. (2008) do not provide estimates for
mountain or lake fed streams in cold dry climates. Instead we used the estimated value for Hill fed
streams in the same climate and geology category.
Table 1. Stream type sub-categories for waterways in the Upper Waitaki and example waterways.
Characteristic
Climate
Topography
Geology
Category
Cool-extremely
Wet
Cool wet
Cool dry
Glacial mountain
Mountain
Hill
Alluvium
Hard sedimentary
Soft sedimentary
Abbreviation
CX
Example
Alpine headwaters
CW
CD
GM
M
H
AL
HS
SS
upper Fraser Stream, Forks Stream, Ahuriri
Otematata River
Alpine headwaters
Fraser Stream, Forks Stream, Ahuriri
Grays River, lower Omarama
Tekapo River, lower Omarama
Upper Omarama, Otematata
Willow Burn
The majority of sites in the upper Waitaki catchment had median dissolved reactive phosphorus values
within the estimated reference value range for that stream type (Appendix 1; table 1). The exceptions
were the Omarama Stream (100 % increase due to anthropogenic contribution; ref. condition 0.003
mg/l, measured median 0.006 mg/l), Sutherlands Creek (133 %), Willow Burn at Benmore Boundary
(50 %), Willow Burn at Glens boundary (200 %), the Willow Burn at Quailburn Rd Bridge (166 %) and
the Hen Burn at Henburn rd (33 %) . However, in terms of total phosphorus all sites had measured
median values in excess of the estimated reference median (Appendix 1; table 1). Streams with
notably high total phosphorus were the Willow Burn, Quail Burn, Sutherlands Creek, Omarama Stream
and Mary Burn at state highway 8.
McDowell et al. (2013) did not calculate reference values for mountain or glacial mountain streams
due to a lack of data. However, it is well known that many such streams and rivers naturally carry a
high fluvial sediment load due to the Southern Alps being in an active erosion state (Griffiths 1979).
Therefore, there is the potential for such rivers to naturally contribute elevated total phosphorus
loads. However, the alpine rivers monitored in the upper Waitaki catchment, such as the Ahuriri and
Tekapo rivers (strictly speaking lake fed at the sampling point but with some glacial flour in
suspension) had measured total phosphorus levels close to the estimated reference median based on
Hill fed rivers. In addition we acquired phosphorus data from NIWA for the Haast River at Roaring Billy.
The Haast River is a large glacial alpine river which carries a substantial load of glacial flour derived
from the same alpine geology as the headwaters of the Waitaki Zone river’s. As such we have assumed
that the Haast River is a suitable proxy for the Waitaki headwaters, such as the Godley, Tasman,
Dobson and Hopkins rivers. In the Haast River the concentration of DRP is consistently at or less than
0.006 mg/l (Figure 4). Occasional, spikes in total phosphorus presumably associated with high flow
events are apparent. However, despite occasional very high total phosphorus ( ~2 mg/l) DRP remains
low. The data presented in figures 2 and 4 suggests that despite the high levels of suspended
particulates found in the Haast River and many Waitaki River head waters this phenomena does not
generally result in elevated dissolved reactive phosphorus.
Figure 4. The [lack of a] relationship between dissolved reactive phosphorus (DRP) and total
phosphorus (TP) between April 1989 and June 2014 in the Haast River at Roaring Billy.
Rather, inspection of Appendix 1 shows that the streams with particularly high phosphorus were those
with lower river gradient and a significant groundwater contribution to their flow, such as the Willow
Burn, Quail Burn and Hen Burn. Presumably the elevated sediment and total phosphorus found in
these streams is derived from land use activities in the catchment as opposed to natural processes.
The absence of elevated phosphorus in the glacial rivers despite naturally high suspended sediment
loads can be attributed to the very low levels of phosphorus contained within the metamorphic
greywacke rock formations of the Southern Alps.
Summary
Both dissolved reactive and total (dissolved + particulate) phosphorus are used as indicators of trophic
status in streams although there is some controversy over which measure is the most appropriate.
Dissolved reactive phosphorus is usually considered to be the best indicator of the immediately plant
available fraction, but due to rapid cycling, and the inclusion of organic phosphorus, total phosphorus
is probably a better indicator of overall phosphorus nutrient status.
Natural phosphorus supply from the catchment to streams is typically sporadic. Both dissolved and
particulate forms are in low/very low supply during stable flow. However, significant quantities,
particularly of particle bound phosphorus, can be flushed into streams during high flow storm events.
Stored phosphorus in stream bed sediments may represent the primary source of measured dissolved
reactive phosphorus concentrations in streams at low flows. Phosphorus in sediments diffuses from
areas of high concentration into low concentrations in water. This equilibrium reaction can maintain
the dissolved reactive phosphorus concentration over and above supply from the catchment. Plants
and algae also have various other mechanisms to extract phosphorus from the particulate store.
An excess of sediment bound phosphorus retained by streams may result in a lag between the
cessation of anthropogenic phosphorus supply in a stream and the reduction in measured stream
concentrations.
Land use intensification may significantly increase the supply of phosphorus to waterways. Dissolved
reactive and organic phosphorus may enter streams through surface and subsurface drainage.
Particulate bound phosphorus enters streams through surface runoff and bank erosion/trampling by
stock.
Although phosphorus supply and cycling in streams is complicated, reference phosphorus conditions
have been estimated for the upper Waitaki catchment using broad scale climate, topography and
geology (McDowell et al. 2013). All measured total phosphorus median values at water quality sites
in the upper Waitaki exceeded nationally estimated reference values. Measured DRP medina values
were typically below the modelled reference value, except in four streams; the Willow Burn, Hen Burn,
Sutherlands Creek and Omarama Stream. The spring-fed streams showed the greatest anthropogenic
contribution.
References
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Appendix 1
Table 1. Water quality monitoring sites in the upper Waitaki catchment, reference (upper 95th % confidence interval) and measured median values for
dissolved reactive phosphorus and total phosphorus. *There was inadequate data to estimate reference values for mountain and lake fed streams in the
catchment and so the reference values estimated for Hill fed stream was used instead.
Water quality monitoring site
Site
Number
LWRP river type
REC stream characteristic
Source of
Geology
Climate
flow
Dissolved Reactive phosphorus
Total phosphorus
Reference value
Measured median
TP
Measured median
AHURIRI RIVER SH8 BRIDGE
SQ20881
Alpine upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.007
Omarama Stream (SH8) Site No:
SQ10005
Hill-fed lower
Hill
Hard
Sedimentary
Cold Dry
0.003 (0.005)
0.006
0.006 (0.008)
0.016
Sutherlands Creek Ben Omar Rd No:
SQ10037
Spring-fed upland
Hill
Hard
Sedimentary
Cold Dry
0.003 (0.005)
0.007
0.006 (0.008)
0.029
Upper Wairepo Creek
SQ10852
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.029
Cold Dry
0.004 (0.007)
0.006
0.008 (0.015)
0.029
Willowburn Benmore Boundary
SQ10853
Spring-fed upland
Hill
Soft
sedimentary
Willowburn Glens Boundary
SQ10854
Spring-fed upland
Hill
Soft
sedimentary
Cold Dry
0.004 (0.007)
0.012
0.008 (0.015)
0.069
Willowburn Above boundary
SQ35657
Spring-fed upland
Hill
Soft
sedimentary
Cold Dry
0.004 (0.007)
0.002
0.008 (0.015)
0.018
Willowburn Boundary
SQ10855
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.003
0.005 (0.008)
0.016
Willowburn Trib Buscot
SQ10856
Hill-fed lower
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.003
0.005 (0.008)
0.017
Willowburn Quailburn Rd Bridge
SQ10012
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.008
0.005 (0.008)
0.031
Quailburn @ Quailburn Rd
SQ10826
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.015
Quailburn Recorder
SQ35792
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.003
0.005 (0.008)
0.016
Quailburn @ Henburn Rd:
SQ10823
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.003
0.005 (0.008)
0.012
Henburn @ Hunburn Rd Site
SQ10824
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.004
0.005 (0.008)
0.018
Mountain*
Hard
Sedimentary
Cold Dry
0.003 (0.005)
0.002
0.006 (0.008)
0.007
Otematata River SH83
SQ10301
Alpine upland
Spring Creek SH8
SQ10206
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.007
Spring Creek Glenbrook
SQ10851
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.007
Wairepo Creek Arm Inlet
SQ10804
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.009
Bendrose Stream SH8
SQ10266
Spring-fed upland
Mountain*
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.007
REC stream characteristic
Water quality monitoring site
Site
Number
LWRP river type
Dissolved Reactive phosphorus
Total phosphorus
Source of
flow
Geology
Climate
Reference value
Measured median
TP
Measured median
Twizel River SH8 Bridge
SQ10272
Alpine upland
Mountain*
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.007
Twizel River - Lower
SQ35119
Spring-fed upland
Mountain*
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.007
Fraser Stream
SQ10803
Alpine upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.007
Forks Stream SH8
SQ26368
Alpine upland
Mountain*
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.007
Grays River Lower Above Ford
SSQ35117
hill-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.005
0.005 (0.008)
0.007
Tekapo River above Grays River
SQ26848
Lake fed
Lake*
Hard
Sedimentary
Cold
extremely
wet
0.004 (0.005)
0.002
0.004 (0.006)
0.007
Tekapo River Steel Bridge
SQ20785
Lake fed
Lake*
Alluvium
Cold wet
0.003 (0.005)
0.002
0.004 (0.006)
0.007
Maryburn SH8 Bridge
SQ10275
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.014
Mary Burn Fill
SQ26372
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.007
Maryburn Stream Lower Tekapo River
SQ35115
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.0025
0.005 (0.008)
0.008
Irishman Creek SH8
SQ26369
Spring-fed upland
Hill
Alluvium
Cold Dry
0.003 (0.005)
0.002
0.005 (0.008)
0.007