Participant research/application experiences

A question of place?

We would like invite research teams that have described “spatial variability” in nutrient fluxes at any scale from the field to the basin to share their experiences.  We will attempt to synthesize what we get and report back to the group. We need to further clarify what we mean by spatial variability and distinguish it from the extensive literature describing the diversity of diffuse pollution sources.  What we are seeking to establish is whether the landscape sources of diffuse pollution are more additive or more dependent on spatial relationships (in which case you can not simply total emission sources in the landscape to calculate the basin load).  In fact the question is probably not this simple.  A better question might be: under what conditions are pollution sources not additive so that understanding landscape position and connectivity become important to understanding watershed and basin loading of pollutants?  A related question that came up in the discussion was: why do we assume that best management practices are additive in the landscape?  In this case, knowing spatial dependencies might become important in optimizing the placement of BMPs.

We have listed some questions below.  If you could copy and paste these questions into a word processing program, answer the questions that seem appropriate to your work, and then copy and paste back into a comment/reply to this post (or email if you prefer), we will then read, collate, and attempt a summary and synthesis.  In the first comment, Dr. Dorioz has provided answers to the questions from his research experience, as an example.

Questions about your study:

Project name and contact:

BACKGROUND

Location:

General Climate:

Landform/topography:

Detailed description (if you want to specify):

Water quality parameters:

Water quality issue:

Scientific/Management questions:

Scale (field, farm/group of fields, watershed, basin):

Comments on scale and approach (optional):

Land use diversity in treatment/study area:

Important agricultural practices in treatment/study area:

Mass balance considerations (rough):

Literature reference:

ROLE OF LANDSCAPE PATTERNS AND SPATIAL RELATIONSHIPS (FROM YOUR WORK)

Does your work suggest that emissions of diffuse pollutants are additive or not:

If areas that you expect would have high diffuse exports don’t meet that expectation, what do you suspect are the major causes of the reductions:

Are there any areas where the pollutant load to receiving surface waters exceeds your expectation (pollutant flux in excess of loading values):

What seem to be the most important landscape features modifying the site-level source emission (under any conditions, e.g. extreme storm flows, snow melt runoff, base flow):

About Deane Wang

I teach courses relating to ecology and education including conservation, sustainability, greening infrastructure, teaching in higher education, and race and culture for first year students. Working with graduate students (ecological planners and field naturalists), I emphasize service-learning and experiential learning. I also have supported an undergraduate summer service corps called LANDS (www.uvm.edu/~conserve). My research has been on biogeochemistry and nutrient cycling at the ecosystem and landscape levels, and more recently on sustainability and education. I have been a research associate at Yale and the Institute for Ecosystem Studies, an assistant professor at the University of Washington, and an associate and acting dean at the Rubenstein School of Environment and Natural Resources.
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3 Responses to Participant research/application experiences

  1. Jean-Marcel Dorioz says:

    Project name and contact:
    Phosphorus reduction strategy Lake Léman Basin and other large French Peri-alpine Lake Basins, Jean-Marcel Dorioz (dorioz@thonon.inra.fr)

    BACKGROUND

    Location:
    Haute Savoie, France

    General Climate:
    temperate, moderate rainfall intensity, relatively dry period in summer snow pack in winter (above 700 m elevation)

    Landform/topography:
    Agricultural areas: large valleys and hilly areas (altitude range from 400m to 12OOm)

    Detailed description (if you want to specify):
    The head of the lake basin (elevation >1300m) is a rather undisturbed mountainous area (forests, high altitude vegetation ….) while the areas close to the lake (range in elevation: 400-1000m) are developed and consist of both rural and urbanised landscapes.

    Water quality issue:
    key words: eutrophication; nutrients; diffuse pollution; agricultural sources.
    Eutrophication of peri-alpine lakes such as Lake Léman began to be obvious in the 60’s. Policies to control P loads to surface waters have been implemented since the 80’s, and have led to significant improvements costing some billions of euros. Once the water quality began to improve (>1990), the number and quality of ecosystem services expected from the lake increased (water supply for all the cities situated on the shore, biodiversity and habitat, recreation, etc.) The expectation that these services will be maintained combined new concerns about climatic change impacts on surface water and lake ecosystem recovery has reinforced the need for a renewed emphasis on the control of nonpoint phosphorus.

    Water quality parameters:
    TP, DRP, TSS, NO3 (concentration and fluxes)

    Scientific/Management questions:
    Renewed concern for lake ecosystem health has led managers working with scientists to develop a set of operational questions about diffuse agricultural sources of P: (1) how does total-P originating from agricultural lands contribute to eutrophication? (2) how can we achieve sustainable reductions in P in a rapidly changing context (development, global change, food scarcity, etc.)? (3) are the BMPs designed for more intensively cultivated areas all over the world, implementable in our specific rural context? 

    Scale (field, farm/group of fields, watershed, basin):
    Complementary studies were performed at different landscape scale: fields (ha); group of fields forming “landscape units” (10 ha); watershed (100 -1000 ha); sub-basin (30 000 ha, representative of rural areas)

    Comments on scale and approach (optional):
    Scale for expected operational findings: managers expectations were to obtain a global understanding of the low land agricultural areas , to allow relevant action to be taken in the context of land planning and development; consequently we had to provide operational answers (via a scientific research program) valuable for the whole lake basins (a regional scale 300 -500 km2).

    Land use diversity in treatment/study area:
    Land cover ( agricultural fields; forests; wetlands; urban; roads ; natural vegetations)
    Soils (soil type; P olsen content, surface permeability)
    Agricultural practices (land uses, tillage practices, fertilization, machinery ,farm work planning, P mass balances)

    For the studied sub basin (30,000 ha): Usable Agricultural areas: 18,000 ha (100%)
    Hay fields 40%
    Pastures 20%
    tilled fields (corn, wheat, colza/rape seed, soybean, sunflower) 37%
    vineyards 1%
    orchards 1%
    divers 1%

    Important agricultural practices in treatment/study area (optional):
    20% of individual farms are traditional dairy farms (relatively extensive, 30 ha, 30 cows, 3/4 land as grasslands, and low P inputs)
    40% are relatively intensive dairy or cash crops farms (80-100 ha, 80 cows, corn fields, silage and/or cash crops, high fertilizer and artificial food inputs)
    40% intermediary case (dairy farms or mixed crop-livestock farms, 50 ha, 60 cows with more than half in tillage)

    Mass balance considerations (rough):
    usual loading values
    grasslands 0.2 to 0.5 kgP/ha/yr
    cereals 0.3 to 2.5 kgP/ha/yr
    natural forested areas < 0.2 kgP/ha/yr
    P mass balance of tilled fields: excess of P inputs from 0 to 30 kgP/ha/yr (varies according to the farming system)

    Literature reference:

    JORDAN-MEILLE L et DORIOZ JM-2004 – Soluble phosphorus dynamic in an agricultural watershed  Agronomie (2004) 237-248.
    DORIOZ J. M., QUETIN P., LAZZAROTTO J., ORAND A. (2004). Bilan de Phosphore dans un bassin versant du lac Léman : conséquences pour la détermination de l’origine des flux exportés. Revues des Sciences de l’Eau 17(3) : 329-354.
    DORIOZ J.-M., WANG D., POULENARD J., TREVISAN D., 2006 – The effect of grass buffer strips on phosphorus dynamics – A critical review and synthesis as a basis for application in agricultural landscapes, in France. Agric. Ecosyst. Environ., 117, p. 4-21
    TREVISAN D., VANSTEELANT J.Y., DORIOZ J.M., 2002. Survival and leaching of fecal micro-organisms after slurry spreading on mountain hay meadows : consequences for the management of water contamination risk. Water Research, 36, 275-283.
    Wang D., Dorioz J.M., Trevisan D., Braun D.C., Windhausen L.J., Vansteelant J.Y., 2003. Using a landscape appraoch to interpret diffuse phosphorus pollution and assist with water quality management in the basin of Lake Champlain (Vermont) and Lac Léman (France) In T.O. Manley and P.L. Manley (eds.) Lake Champlain in the New Millennium . Water Science and Application. Vol. 2. American Geophysical Union.
    VANSTEELANT J.Y., TREVISAN D., PERRON L., DORIOZ J.M., ROYBIN D., 1997. Conditions d’apparition du ruissellement dans les cultures annuelles de la région lémanique, relation avec le fonctionnement des exploitations agricoles. Agronomie, 17, 17-34.
    DORIOZ J.M., CASSEL A., ORAND A., EISENMAN K. 1998 Phosphorus storage, transport and export dynamics in the Foron river watershed. Hydrol. Processes, vol. 12, 285-309
    CRISTOFINI B , PERRIN T ROYBIN D, DORIOZ JM , BAZIN G 1999. "French and european mountains ecosystems lessons drawn and outlook for sustainable development ".In planetary garden 99. Intern. symposium on sustainable ecosystem management Chambery, March 14-18.Ed Savoie technolac Prospective 2100

    ROLE OF LANDSCAPE PATTERNS AND SPATIAL RELATIONSHIPS (FROM YOUR WORK)

    Does your work suggest that emissions of diffuse pollutants are additive or not:
    Not additive in average at the scale of the year.
    Most of individual storm flow events are not additive except some extreme ones.

    If areas that you expect would have high diffuse exports don’t meet that expectation, what do you suspect are the major causes of the reductions:
    The buffer capacity of the landscape system is due to (1) numerous small wetlands connected with the low-order hydrographic stream network – they generally act as a selective filter for total-P; (2) hay fields and coppice inserted into the tilled-field matrix -generally acts like barriers for total P; (3) other buffers, loading reduction efficiency is very variable according to their size (but usually most effective at particulate P reduction), includes hedges, riparian strips, and some fields margins that can act like a vegetated filter strips (these are rare).
    Point (2) is possible in our agricultural landscape where numerous small fields create a mosaic at the sub-watershed/watershed scale. When sediment and nutrient uptake capacity is incorporated into the mosaic as hayfields, hedgerows, coppice, etc., this can limit surface runoff and concentrated flow (which is often difficult to buffer).

    Are there any areas where the pollutant load to receiving surface waters exceeds your expectation (pollutant flux in excess of loading values):
    Yes, locally and at certain times of the year
    Case 1: Critical areas within grazing fields. especially when a set of gateways are directly connected with a road and its ditches or another flow pathways. Around gateways, high temporary livestock densities compact the soil creating a high risk of surface runoff and erosion (higher than the surrounding land use).
    Case 2: Roads and non-agricultural impervious areas distributed throughout our watersheds generate important amounts of runoff (1) which flush out accumulated sediments and their pollutants loads during summer rainfall events (2) which can induce local, intense soil erosion when entering into fields. The occurrence of these phenomena and their associated loads are even more important in areas with urban sprawl.
    Case 3: Arrangements to organize and consolidate ownership of farm fields can lead to large, specialized “landscape units” of mostly tilled fields, effectively increasing field size and the length of ditches (increasing pollutant transfer, bank erosion, etc.) and thus creating a potential for cascading effects on processes of pollutant emission.

    What seem to be the most important landscape features modifying the site-level source emission (under any conditions, e.g. extreme storm flows, snow melt runoff, base flow):
    Topographic position seems most important for dissolved P (most of the bottom slopes of fields generates fluxes of P when the soil is saturated).
    Size and shape/slopes of tilled fields (in relationship with the generation of concentrated runoff) for particulate P.
    Comments: Total-P emission from the fields is mainly governed by the management of soil surface structure (crusting effect) and development of plant coverage of the soil, and consequently distributed in time and space mainly as a result of variability of agricultural practices applied to cultivated fields.

  2. Jim Miller says:

    Project name and contact:
    Lower Little Bow River, Alberta, Canada
    Jim Miller, jim.miller@agr.gc.ca

    BACKGROUND

    * Location: Lower Little Bow watershed, southern Alberta, Canada. Latitude (50º00’00”), Longitude (112º37’30”)

    * General Climate: Semi-arid within mixedgrass prairie region of southern Alberta

    * Landform/topography: Glacial till, glaciolacustrine, and glaciofluvial parent material. The topography is undulating to hummocky on the upland areas with 2 to 9% slopes. The river valley has floodplains and terraces with 0 to 5% slopes and with short risers and banks with slopes > 9%.

    * Detailed description (if you want to specify): Detailed description can be found in published papers: Miller et al. (2010a, b, c).

    * Water quality parameters: TSS, turbidity, DO, temperature, salinity (EC), N fractions (total N, total dissolved N, total particulate N, NO3, NH4), P fractions (total P, total dissolved P, total particulate P, DRP), E. coli, fecal and total coliforms, Enterococcus

    * Water quality issue: Main problems in Lower Little Bow River are sediment (TSS and turbidity), followed by total P, E. coli, and then DO and total N

    * Scientific/Management questions: Evaluate effect of various beneficial management practices on soil and water quality. The BMPs evaluated are off-stream with and without fencing, buffers, conversion to greencover, and manure management (P- vs N-based application).

    * Scale (field, farm/group of fields, watershed, basin): Soil samples to rainfall simulations to field-scale runoff to river

    * Comments on scale and approach (optional): We believe that multi-scale approach is a good method to study the BMPs in this watershed

    * Land use diversity in treatment/study area: Very diverse from dryland annual cropping (wheat, barley) to intensive irrigated cropping (corn, barley, tame pasture) to dryland native rangeland with some intensive livestock operations.

    * Important agricultural practices in treatment/study area: Dryland and irrigated farming, intensive livestock operations, irrigation canals and irrigation return flow drains

    * Mass balance considerations (rough): A N and P budget were conducted on the watershed. The watershed had a surplus of 38 kg N/ha/y and 5 kg P/ha/y. Major inputs causing surplus of N were manure, followed by fertilizer and the major P input was manure.

    Literature reference:
    Miller, J., D. Chanasyk, T. Curtis, T. Entz, and W. Willms. 2010. Influence of streambank fencing with a cattle crossing on riparian health and water quality of the Lower Little Bow River in southern Alberta, Canada. Agric. Water Manage. 97:247-258

    Miller, J.J., T.W. Curtis, E. Bremer, D.S. Chanasyk, and W.D. Willms. 2010. Soil test phosphorus and nitrate adjacent to artificial and natural cattle watering sites in southern Alberta. Can. J. Soil Sci. 90:331-340.

    Miller, J.J., D.S. Chanasyk, T. Curtis, and W.D. Willms. 2010. Influence of streambank fencing on the environmental quality of cattle-excluded pastures. J. Environ. Qual. Doi:10.2134/jeq2009.0233.

    ROLE OF LANDSCAPE PATTERNS AND SPATIAL RELATIONSHIPS (FROM YOUR WORK)

    * Does your work suggest that emissions of diffuse pollutants are additive or not:
    I don’t think we have enough evidence to support this conclusion and our study was not set up to study the additive objective. If I had to guess, I would say that emissions are likely reflecting cumulative additions over time.

    * If areas that you expect would have high diffuse exports don’t meet that expectation, what do you suspect are the major causes of the reductions:
    We thought our watershed would have more runoff than expected, and this is likely because of the semi-arid climate and due to modeling indicating that groundwater flow is likely more dominant than runoff. We thought the river would have greater concentrations of soluble nutrients but that is not the case, and we are not sure why. Maybe denitrification in riparian zone or river causes low NO3 in river.

    * Are there any areas where the pollutant load to receiving surface waters exceeds your expectation (pollutant flux in excess of loading values):
    TSS in the river exceeds water quality guidelines and may be related to sediment delivered by irrigation return flow and from bank erosion. We have been measured streambank erosion using erosion pins and have found considerable bank erosion. Sometimes, 1 to 2 feet of a streambanks will break off into the river.

    * What seem to be the most important landscape features modifying the site-level source emission (under any conditions, e.g. extreme storm flows, snow melt runoff, base flow):
    The combination of runoff, groundwater, and irrigation flow are likely controlling diffuse pollution in this watershed. We have also found that most runoff doesn’t occur as sheet flow but rather as preferential flow in channels.

  3. Project name and contact:
    Pike River watershed research program.
    Aubert R. Michaud. IRDA. Quebec
    aubert.michaud,@irda.qc.ca

    BACKGROUND

    Location:
    Pike River basin covers 630 km2 across the Canadian province of Quebec (531 km2) and the Vermont state of USA (99 km2). The basin drains into Missisquoi bay of Lake Champlain (45°02’N and 73°05’W).

    General Climate:
    Humid temperate. Considering the orographic gradient (30 to 710 m), annual mean precipitation vary from 1156-1272 mm, annual mean temperature from 5.8° to 6.8°, and annual mean snowfall from 247 to 390 mm.

    Landform/topography:
    The watershed presents a clear spatial gradient in land-use and landforms. The watershed’s upstream region (390 km²) spanning across the Appalachian piedmont is dominated by sandy and shaly loams, typically humic gleysols and podzols. Elevations range from 50 to 710 m above mean sea level (AMSL), with a 5° mean slope. Given the types of soils and the land’s rugged features, this region is ill-suited for intensive agriculture.

    The watershed’s downstream region (240 km²) draws upon the plains of the St. Lawrence
    lowlands and Appalachians. Clays of marine and lacustrine origin (gleysolic) occupy the low-lying
    areas, whereas calcareous and shaly tills (brunisolic and podzolic) occupy the higher elevations and rolling hills. Elevation ranges from 20 to 130 m AMSL, with flatter slopes (0.6° on average). Three-quarters of the downstream region is cultivated.

    Detailed description (if you want to specify):
    Detailed description can be found in published papers Deslandes et al., 2006 and Michaud et al, 2007).

    Water quality parameters:

    Considering the environmental issue and operational objectives, the research program focus on P fluxes and speciation. Multi-probe sensors are combined with analytical methods. Parameters include TSS, turbidity, temperature, salinity (EC), P fractions (total P, total dissolved P, total particulate P, DRP, Bioavailable-P), N fractions (NO3, NH4).

    Water quality issue:

    A severe impairment of water quality by cyanobacterial blooms in the lake’s northerly-situated Missisquoi Bay led to the governments of Quebec (Canada) and Vermont (USA) reaching a specific agreement on phosphorus loads in the bay. Annual mean total-P concentrations in the bay have consistently exceeded Vermont and Quebec’s water quality criterion of 25 μg P l-1. Phosphorus loads entering the bay were apportioned 60% to Vermont and 40% to Quebec. Given that most of the non-point P load has been linked to agricultural sources, management plans have focused on agricultural best management practices (BMPs) of soil and water resources.

    Scientific/Management questions:

    On-going since 1997, the research program conducted within the Pike River watershed supports plot and field scale experiments, watershed monitoring, remote sensing and hydrologic modeling activities. Through a proactive partnership gathering researchers, extension’s staff and farm managers, the program carries the following objectives 1) to describe the non-point source nutrient transfers to the aquatic ecosystem, 2) to develop user-friendly GIS (Geographic Information System) tactic tool for farmers/extension staff dedicated to the diagnosis and treatment of critical source areas of runoff and diffuse contamination, 3) evaluate the effectiveness of best management practices (BMP’s) at (meso-) watershed scale and 4) develop and validate hydrologic models to asses strategic issues, including optimisation of BMP’s scenarios at basin scale, hydrologic and nutrients transfers trends under climate change and surface water and aquifer recharge interactions.

    Scale (field, farm/group of fields, watershed, basin):

    The research program was undertaken on a wide range of scales: (i) plot scale—testing of effects and interactions of benchmark soils properties, manure inputs and crop cover on P loads and speciation (Michaud et al., 2004a); (ii) field-scale (10 ha)—monitoring of P losses in surface runoff and subsurface drainage waters (Enright and Madramootoo, 2004; Jamieson et al, 2003); (iii) meso-scale (six to ten km2) —characterization of spatio-temporal variability in P fluxes across the watershed (Michaud et al., 2004b; 2009), and assessment of magement effects on water quality through a paired-basin design (Michaud et al., 2009); and (iv) macro-scale (630 km2)—indexation of P transfers (Deslandes et al., 2004).

    Comments on scale and approach (optional):

    Different scales of observations within Pike River basin highlighted different relations between landscape, land use/management and nutrient mass balances as drivers of nutrient fluxes. Macro- (basin) scale and plot scale (rainfall simulator) best highlighted source factors effects on P mobility. Spatial sampling at meso-scale as well as field scale monitoring best described hydrologic and edaphic controls on surface and subsurface transfers of P.

    Macro-scale: Spatial sampling at basin’s macro-scale (630 km2) significantly related nutrient input, land-use gradient and elevation of sampled subwatersheds to stream P levels during peak flow events (Deslandes et al., 2004). Elevation, as a single factor, best explained the spatial variability in P fluxes, but remained also highly (negatively) correlated with agricultural land use and soil P levels. Up to 86% of spatial variability in P fluxes could be explained by combinations of these factors, indicating that both source (soil P stock and input) and transport factors (land use, elevation) were complementary in explaining P mobility. However, since land use, landform, soil P levels and P inputs also followed a similar spatial gradient across the basin (upstream marginal land calls for lower intensity in agricultural systems), the multivariate model did not enable a clear distinction between source and transport factors spatial influences on P mobility. From an operational perspective, the macro-scale enabled a relative ranking of P contributing areas within the watershed, which was useful, strategically, in targeting critical subwatersheds and establishing target P yields. However, the macro-scale offered a limited perspective on interpreting the relative influences of source and transport drivers on P mobility due to correlation in landform and land use and nutrient inputs gradients.

    Meso-scale: A similar spatial sampling protocol was applied to the meso-scale Castors Brook subwatershed (10 km2), the most impaired sub-watershed of Pike Rive basin. The sub-watershed presents a homogeneous agricultural land use and comparable cropping system across its entire surface area. Spatial variability in stream P levels during peak flow event indicated that hydrologic (transport) controls exerted a dominant influence on P mobility (Michaud et al., 2004b). Despite an opposite gradient in soil P levels and P inputs, low-lying clayey catchments demonstrated highest stream P levels as they became saturated earlier on extended near-stream surface in response to elevated stream and water table level. Preferential subsurface P transfers through the tile drainage systems, linked to the nature of the parent material (marine clay deposits), was also identified as a significant driver. However, the spatial pattern observed for stream P did not invalidate the influence of source factors, as P inputs explained significant differences amongst catchments under comparable hydrologic activity.

    A six-year monitoring program on twin watersheds (6-8 km2), with comparable land use and cropping system, indicated similar conclusions regarding the landscape control over P exports. Despite significantly lower P inputs, the watershed occupying the lower position within the landscape exhibited higher P loadings than its upland counterpart (Michaud et al., 2009) due presumably to more active surface hydrological activity.

    From an operational perspective, these meso-scale observations bear an important tactic implication when it comes to identifying critical source areas, namely that the landform features should comes first, before source factors, when targeting best management practices on cropped land.

    Field scale: Monitoring of surface runoff and drain flow from field representative of contrasting landforms, close to Castors Brook watershed experimental site, indicated similar soil and landscape controls on P exports. Low-lying, clayey site demonstrated higher surface runoff P emissions as well as higher loadings in the subsurface drains due to the nature of the subsoil, as compared to the upland, lightly textured site (Enright and Madramootoo, 2004; Jamieson et al, 2003).

    Plot scale: Finally, plot-experiment observations (10 m2) within Castors Brook watershed under artificial rainfall were coherent with the literature on source and crop cover factors effect on P. Under experimental conditions where landscape position and form no longer trigger surface runoff, soil P level and manure inputs were shown to explain P emission in surface runoff, both under bare soil and hay cover (Michaud et al., 2004a). From the perspective of BMP’s implementation, these observations confirmed that the control over soil P build-up and timing of P inputs remain a strategic prerequisite.

    Land use diversity in treatment/study area:
    The watershed’s land-use gradient reflects the landform spatial gradient. Given the types of soils and the land’s rugged features, the watershed’s upstream region region is ill-suited for intensive agriculture. Overall, forest occupies 54% of the region’s area, 22% is devoted to agriculture to perennial forage crops and 13% to annual crops, reflecting the predominance of dairy and swine production (0,44 Animal units-AU/ha). The watershed’s downstream region is more intensively cultivated, with three-quarters of its surface area being cropped. Forest, perennial forages and annual crops occupy respectively, 18%, 24 %and 52% of the downstream part of watershed. Animal production follows the same pattern as in the upstream region of the watershed, albeit more intensively (1,01 Animal units-AU/ha). The downstream region also contains the industrial and population (approximately 9,000) centres of the region.

    Important agricultural practices in treatment/study area:
    Typical crop rotation in dairy agricultural system includes corn, small grain and hay, with liquid manure side-dressed on hay or pre-plant on corn cropped area. Cash crop rotations are based on corn and soya, manured in spring pre-plant period. Conservation tillage accounts for approximately 30% of corn and soybean acreages.

    Most of cropped land (60%) is subsurface drained, while drainage density has been improved to approximately 2km length watercourse/km2. Structural runoff controls have been systematically installed within the downstream part of the watershed, typically in-ditch catch inlets intercepting surface runoff prior to its transfer to the stream.

    Mass balance considerations (rough):
    Over cropped area, manure and mineral P inputs respectively average 14,9 and 8,0 kg P/ha annually. Annual crop uptake averages 14,6 P/ha. Phosphorus mass balance over soil surface thus averages 8,3 kg. Average yearly P flux at watershed’s outlet averages 1,2 kg P/ha.

    Literature reference:

    Deslandes, J., Michaud, A. R. and Bonn, F. 2004. Use of GIS and remote sensing to develop indicators of phosphorus non-point source pollution in the Pike River basin. Pages 271–290 in T. O.Manley, P. L. Manley, and T. B, Mihuc, eds. Lake Champlain: Partnerships and research in the new millennium. Kluwer Academic/Plenum Publishers, New York, NY.

    Deslandes, J., I. Beaudin, A. R. Michaud, F. Bonn and C. A. Madramootoo. 2006. Influence of landscape and cropping system on phosphorus mobility within the Pike River watershed of Southwestern Quebec. Canadian Water Resources Journal 32(1): 21-42.

    Enright, P. et C.A. Madramootoo. 2004. Phosphorus Losses in Surface Runoff and Subsurface Drainage Waters on Two Agricultural Fields in Quebec. P. 160-170. in R.A. Cooke (ed.) Drainage VIII –Proceedings of the Eight International Drainage Symposium. Published by ASAS –St. Joseph, MI, USA.

    Jamieson, A., C.A. Madramootoo and P. Enright. 2003. Phosphorus losses in surface and subsurface runoff from a snowmelt event on an agricultural field in Quebec, Canadian Biosystems Engineering, Vol. 45, pp. 1.1-1.7.

    Kroeger, A.C., C. A. Madramootoo, P. Enright, C. Laflamme. 2009. Les marais filtrants: une solution pour restaurer les cours d’eau agricoles. Agrosolutions 20 :1 pp.4-14.

    Michaud, A.R. et M.R. Laverdière. 2004a. Effects of cropping, soil type and manure application on phosphorus export and bioavaibility. Canadian Journal of Soil Science, 38: 295-305. Erratum 84 (4) p. 525.

    Michaud, A.R., R. Lauzier and M.R. Laverdière. 2004b. Temporal and Spatial Variability in Nonpoint Source Phosphorus in Relation to Agricultural Production and Terrestrial Indicators: the Beaver Brook Case Study. In Lake Champlain: Partnerships and Research in the New Millenium. Manley, T.O., P.L. Manley and T.B. Mihuc (Eds.). Kluwer Academic/Plenum Pub. New York, NY, 97-121.

    Michaud, A.R., I. Beaudin, J. Deslandes, F. Bonn et C. A. Madramootoo. 2007. SWAT-predicted influence of different landscape and cropping systems alterations on phosphorus mobility within the Pike River watershed of South-western Quebec. 2007. Canadian journal of soil science 87(3) 329-344.

    Michaud, A.R., M. Giroux, C., J. Deslandes, I. Beaudin et R. Lauzier. 2009a. Prévention des transferts diffus de phosphore en bassins-versants agricoles : perspectives québécoises et de l’État du Vermont. Océanis • vol. 33-1/2 • 2007 • p. 285-320 ISSN 0182-0745 © Institut océanographique, fondation Albert Ier, prince de Monaco.

    Michaud, A.R, S.-C. Poirier, J. Desjardins, Grenier, M., et I. Saint-Laurent. 2009b. Évaluation des exportations de surface et souterraines de phosphore en sol drainé. Rapport final de projet. Institut de recherche et de développement en agroenvironnement (IRDA) et MAPAQ, Québec, Québec, 39 p. http://www.irda.qc.ca/resultats/publications/194.html

    ROLE OF LANDSCAPE PATTERNS AND SPATIAL RELATIONSHIPS (FROM YOUR WORK)

    Does your work suggest that emissions of diffuse pollutants are additive or not:

    From our work in Pike River watershed, landscape and soil properties have been shown to explain a significant part of the spatial variability in P transfers. No doubt that landscape features exert a determinant effect on both P emissions in surface runoff, as well as P transfers in tile drains under the land forms and land use conditions prevailing in Pike River watershed. On the other hand, we did not collect any evidence on a buffering effect of landscape features on incoming P transfers from upstream areas. In fact, the farmland of the study area presents a relatively homogeneous and elevated drainage density (2 km/km2). Historically, the hydraulic capacity of the streams have been systematically improved to accommodate the implementation of tile drainage systems. The hydrology of these catchments have thus been totally modified from initial, natural condition to favour a rapid evacuation of excess water in early spring. This systematic land development responded to the evidence that land drainage was the most important limiting factor for crop production under the prevailing short growing season.

    Considering the efficiency and the systematic implementation of surface and surface drainage systems, it is unlikely that landscape features exert a significant buffering effect on P transfers on farm land of the study area. This suggest that emissions of diffuse pollutants, although highly variable across different landforms, are also additive when being transferred from a landscape units to another. An exception would be related to natural wetlands that have not been altered within the Pike River basin. Such influence of natural wetlands on P transfers have not been assessed within the study area. However, the dynamics of P retention within a network of created wetlands implemented on a tributary to Pike River has been documented by Kroeger et al. (2009). The stream monitoring indicated a significant P retention attributed to the man made landscape features.

    If areas that you expect would have high diffuse exports don’t meet that expectation, what do you suspect are the major causes of the reductions:

    From a macro-scale, Pike River basin perspective, slope gradient was negatively related to stream P. This is conflicting with the literature linking slope gradient to erosive and particulate P transport processes. In fact, subwatersheds associated to higher slope gradient also occupy higher elevations within the landscape, have less intensive land use and receive less P inputs. Although the scale of study makes it difficult to distinguish the relative influence of correlated explaining (source and transport) variables, these observations nevertheless indicate that the landscape exerts its dominant influence on P transfers through the triggering of saturated runoff zones (VSA hydrology) rather than through its relief-related erosive potential.

    From the meso-scale study of Castors Brook sub-watershed, catchments with highest soil P levels did not yield elevated P loadings. This is conflicting with the literature and rainfall simulation studies within the study area linking elevated P concentration in surface runoff to soil P status. In fact, relatively low P yields on these catchments were associated to the permeable nature of subsoil and relatively high position occupied by the catchment within the sub-watershed.

    Are there any areas where the pollutant load to receiving surface waters exceeds your expectation (pollutant flux in excess of loading values):

    Synchronic monitoring of tile drainage systems and surface runoff indicated relatively elevated concentration of particulate (colloidal) biovailable P in subsurface drainage waters entering the stream during peak flow events (Michaud et al., 2009b). These observations call for a reallocation of P transfers related to surface runoff and tile drainage within catchments dominated by tile drainage systems and clay subsoil susceptible to preferential flow.

    What seem to be the most important landscape features modifying the site-level source emission (under any conditions, e.g. extreme storm flows, snow melt runoff, base flow):

    The most important landscape feature with respect to surface P emissions is the relative position occupied by the catchment within the watershed. Proximity and connectivity to stream, elevated water table, convergent stream flow paths and flow accumulation from upstream catchments all contribute to a relatively more intense surface runoff activity in low-lying areas. This influence is relatively more important during the abundant early spring runoff events, when the water table is elevated. During high-intensity summer rainfall events, soil surface conditions, conductive to soil crusting are more likely to exert an influence on infiltration controlled (Hortonian) runoff.

    Regarding subsurface P transfers, soil properties play a dominant role. Clayey gleysolic subsoils have been related to significant P transfers in tiled drained fields (up to 40% of annual total P yield).

    Aubert Michaud
    IRDA, Quebec, Canada
    Irda.qc.ca

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