Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Branger, Flora

Braud, Isabelle

Debionne, Samuel

Viallet, Pierre

English

Hydraulic Engineering Repository

Conference Paper, Published VersionBranger, Flora; Braud, Isabelle; Viallet, Pierre; Debionne, SamuelModelling the Influence of Landscape ManagementPractices on the Hydrology of a Small AgriculturalCatchmentZur Verfügung gestellt in Kooperation mit/Provided in Cooperation with:Kuratorium für Forschung im Küsteningenieurwesen (KFKI)Verfügbar unter/Available at: https://hdl.handle.net/20.500.11970/110215Vorgeschlagene Zitierweise/Suggested citation:Branger, Flora; Braud, Isabelle; Viallet, Pierre; Debionne, Samuel (2008): Modelling theInfluence of Landscape Management Practices on the Hydrology of a Small AgriculturalCatchment. In: Wang, Sam S. Y. (Hg.): ICHE 2008. Proceedings of the 8th InternationalConference on Hydro-Science and Engineering, September 9-12, 2008, Nagoya, Japan.Nagoya: Nagoya Hydraulic Research Institute for River Basin Management.Standardnutzungsbedingungen/Terms of Use:Die Dokumente in HENRY stehen unter der Creative Commons Lizenz CC BY 4.0, sofern keine abweichendenNutzungsbedingungen getroffen wurden. Damit ist sowohl die kommerzielle Nutzung als auch das Teilen, dieWeiterbearbeitung und Speicherung erlaubt. Das Verwenden und das Bearbeiten stehen unter der Bedingung derNamensnennung. Im Einzelfall kann eine restriktivere Lizenz gelten; dann gelten abweichend von den obigenNutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte.Documents in HENRY are made available under the Creative Commons License CC BY 4.0, if no other license isapplicable. Under CC BY 4.0 commercial use and sharing, remixing, transforming, and building upon the materialof the work is permitted. In some cases a different, more restrictive license may apply; if applicable the terms ofthe restrictive license will be binding.MODELLING THE INFLUENCE OF LANDSCAPE MANAGEMENT PRACTICES ON THE HYDROLOGY OF A SMALL AGRICULTURAL CATCHMENT Flora Branger1, Isabelle Braud2, Pierre Viallet3 and Samuel Debionne41 Researcher, Cemagref, Hydrology Hydraulics Research Unit, 3 bis quai Chauveau, 69336 Lyon Cedex 9, France, e-mail: flora.branger@cemagref.fr2 Senior Researcher, Cemagref, Hydrology Hydraulics Research Unit, 3 bis quai Chauveau, 69336 Lyon Cedex 9, France, e-mail: isabelle.braud@cemagref.fr3 Researcher, Hydrowide, 1025 rue de la Piscine, 38400 St Martin d’Hères, France , e-mail: viallet@hydrowide.com4 Researcher, Hydrowide, 1025 rue de la Piscine, 38400 St Martin d’Hères, France , e-mail: debionne@hydrowide.comABSTRACT A distributed hydrological model dedicated to the assessment of the influence of the influence  of  landscape  management  practices  on  the  hydrology  a  small  agricultural catchments is presented. It was built using an environmental modelling framework named LIQUID. The model consists of interconnected modules representing the major hydrological processes in subsurface-drained fields, non-drained fields, hedgerows and in the hydrographic network, and uses an irregular mesh that reproduces the real shapes of the different landscape features.A model prototype was applied to the Fontaine du Theil experimental catchment (1.28 km²) in France. A six month simulation was performed in a winter period. The first results are physically  consistent,  in  spite  of  limitations  for  simulating  the  seasonal  variation  of  the discharge at the catchment outlet. Therefore we can consider that the modelling options that were chosen are promising. Keywords: distributed hydrological model, modelling framework, landscape management practices1. INTRODUCTIONIn small agricultural watersheds, landscape management practices such as subsurface drainage,  ditches  or  hedgerows  affect  considerably  the  different  water  pathways,  with possible repercussions on river regimes or water quality. For example, tile drainage lowers the water table and reduces surface runoff, but is also responsible for fast water flow in the soil with a direct connection to the hydrographic network; ditches intercept surface and subsurface flows with also a fast connection to the river.In order to assess the various influences of these landscape features at the catchment scale, appropriate modelling tools are required. In particular, these models should be able to represent  explicitly  all  important  landscape  features,  including  their  space  locations  and shapes, which may be particularly important for the hydrological response. The governing processes in each element should also be represented with an appropriate time discretization. The structure of the model must also be flexible enough to allow the addition/removal of some features, in order to evaluate their influence. However, most existing models are not well adapted to such representations: classically, distributed hydrological models are based on regular grid meshes and rely on one or two main governing equations and a unique time step.The objective of this paper is to present a first prototype of an alternative modelling approach which represents hydrological systems at the closest of what they are in reality. It uses  explicit  representations  that  are  defined  as  hydro-landscapes  by  Dehotin  and  Braud (2008) and that are, in our case, the different landscape features that can be found in North Western France watersheds (agricultural fields, tile-drained zones, hedgerows, ditches…).2. MODEL PRESENTATION2.1 The LIQUID modelling frameworkThe  model  was  implemented  using  a  framework  for  multi-scale  hydrological modelling named LIQUID (Viallet et al., 2006). It allows the design, implementation and run of models as collections of temporally and spatially interconnected modules. Within the framework, each module represents a specific hydrological process or a set of processes in a particular hydro-landscape. It has its own process conceptualization, and is associated to a GIS vector layer describing the hydro-landscape geometry. The latter can take any shape such as lines or polygons. The model mesh is extracted from these geometries so that the modules can be connected spatially.Each module computes its own state variables and exchange variables thanks to an event-driven mechanism. It is also able to compute its own time step according to internal criteria,  schedule  its  next  execution  in  a  common-shared  calendar,  and  cancel/reschedule executions  whenever  required  by  changes  in  its  inputs.  This  system  allows  a  proper scheduling and synchronized data exchanges during a simulation. More details can be found in Branger (2007).SIDRA/SIRUPTile-drained zonesFRER1DNon-drained zonesHEDGEHedgerowsRIVER1DDitch and sream networkWTISaturated flow exchangesWTRIRiver-groundwater flow exchangesRainfall, Potential Evapotranspiration Stream level and dischargeDrainage dischargeFigure 1: Constitutive elements and data flow diagram of the model.2.2 Modules for hydrological processes in the different hydro-landscapesThe model involves four modules as represented in Figure 1. Each module is dedicated to the representation of the hydrological processes governing a particular hydro-landscape. All the modules have different process conceptualizations.The SIDRA/SIRUP module allows to simulate the outputs of a tile-drained zone (ie drainage discharge and surface runoff). It is based on a spatial integration of the Boussinesq equation for the saturated zone, and a simplified capacity-based approach for the unsaturated zone as shown in Figure 2 (Branger et al., 2008).RechargeDrainage dischargeSurface StorageDeep storageRunoffSurface runoffPET RainfallSaturated zoneUnsaturatedzoneBoussinesq equationFigure 2: the SIDRA/SIRUP module for tile-drained zones.The FRER1D module represents vertical infiltration and evapotranspiration in non-drained agricultural zones using a 1D resolution of the Richards equation (Ross, 2003). It is also adapted for receiving lateral flow in the saturated zone thanks to a source/sink term Q(z,t) (Eq.1). The soil properties are described using the Brooks and Corey (1964) soil coefficients (Eq.2).),(1)( tzQzhhKzt+ −∂∂∂∂=∂∂ θ(1))1();1( elsehhifKKelsehhifhheSSeeS<=<=− ηλθθθθ(2)where  θS is  the  saturated  water  content,  he the  pressure  and  KS the  saturated  hydraulic conductivity.The HEDGE module is a conceptual module which allows to simulate the water table dynamics  and evapotranspiration processes below hedgerows, following the approach that was developed by Viaud et  al.  (2005). It  is  also adapted for receiving lateral  flow in the saturated zone (Figure 3).At last, the RIVER1D module is a simplified flow routing module for the ditch and river  network.  It  is  based  on  the  1D  kinematic  wave  approximation.  Flow  velocity  is computed using the Manning relation. The river network is divided into several reaches with trapezoidal cross-sections that can receive lateral surface and subsurface flows.retention porositydrainage porosityRainfall Surface runoffinfiltrationrechargeEvapo-transpirationWater table levelLateral subsurface flowFigure 3: the HEDGE module for hedgerows. The soil is described by its porosity, which is conceptually divided into retention porosity (immobile water) and drainage porosity (mobile water).2.3 Flow exchanges between the modulesIn order to realize the spatial coupling between the different modules, flow exchange interfaces were added to the model (Figure 1). These interfaces allow to compute saturated lateral flow between the different hydro-landscapes in the catchment.The saturated flow between agricultural fields and/or hedgerows is computed in the WTI  (for  water  table  interface)  interfaces,  using  the  Darcy  law  and  a  simplified parameterization.212121ddHHAKQ+−××=→ (3)where K is the saturated hydraulic conductivity, A the contact area between the two fields, H1 and H2 the water table levels in the fields, d1 and d2 the distances between the fields and the interface.The saturated flow between agricultural  fields/  hedgerows and the river  reaches  is computed in the WTRI (for water table  river interface)  interfaces,  using the Miles (1985) approach:HCKQ mriver ∆××=→  close to the river, (4)where K is the saturated hydraulic conductivity, Cm the Miles coefficient (depending on the geometrical configuration and the water depth in the river reach) and ΔH the head loss of the water table close to the river;( )lHDHHDKQ wriverwriver∆+⋅+∆−×=→5.0)(  far from the river,  (5)where K is the saturated hydraulic conductivity, Dw the difference between the water table level and the level in the river, ΔH the head loss of the water table close to the river, Hriver the water level in the river and l the distance between the river and the field.3. MODEL APPLICATION AND RESULTS3.1 Application case : the Fontaine du Theil experimental catchmentThe first prototype of this model was applied to the Fontaine du Theil catchment (1.28 km²), which is located in Brittany, in North-Western France (Figure 4). The catchment was instrumented from 1998 to 2006 by Arvalis and UIPP for the assessment of non point source pesticide pollution. The hydrological monitoring consists of daily precipitation measurements in one rain gauge and discharge measurements at the catchment outlet at a 5 minutes time step. Geographical data (50 m digital elevation model, land use maps) are also available on the catchment.The  climate  is  oceanic  with  average  annual  precipitations  of  800  mm  regularly distributed along the year. The average annual discharge is 0.018 m3/s. The soils are quite homogeneous,  silty  clayed,  and  lie  on  a  shallow  schistose  bedrock.  The  catchment  is dominated  by agricultural  activity  (dairy farming  and cereals).  The agricultural  fields  are rather  small  (maximum 0.08 km²)  and the landscape presents many specific  management features such as tile-drained zones, and a dense hedgerow network (Figure 4).Nnon-drained agricultural fieldstile-drained agricultural fieldshedgerowsriver network0 0.2 0.4 kmFigure 4: Location and main characteristics of the Fontaine du Theil experimental catchment in France.3.2 Model parameterizationThe mesh of the model follows exactly the limits of the agricultural fields (Figure 4). As a consequence, the model involves 4 tile-drained fields (SIDRA/SIRUP), 81 non drained fields (FRER1D) and 82 hedgerows (HEDGE). The modules parameters were set as simply as possible according to the available field data and literature data. In particular, uniform values were used for describing the soil properties in each module. The main parameter values are reported in Table 1.A six-month simulation was performed during a winter period (October 1998-April 1999). The cumulative rainfall and potential evapotranspiration are respectively 539 mm and 149 mm for this period. The initial conditions were analogous for all the soil modules, with a water  table  level  about  1.5  m below the  soil  surface.  It  corresponds roughly to  the  field observations  at  the  end  of  the  summer  (although  no  measurements  are  available  for  the selected simulation period).Table 1 Parameter sets for the different modules.FRER1DSat. hydraulic conductivity (ms-1)η (-) he (m) λ (-) θs (-)1.2∙10-5 5.8 -0.3 0.8 0.46SIDRA/SIRUPSat. hydraulic conductivity (ms-1)Drainable porosity (-)9.8∙10-6 0.01HEDGERetention porosity (-) Drainage porosity (-)0.147 0.147RIVER1DManning roughness (m-1/3s)0.03WTI/WTRISat. hydraulic conductivity (ms-1)1.0∙10-43.3 Simulation resultsThe simulation results are presented in Figures 5, 6 and 7. The global behaviour of the model is not fully satisfactory, but yet encouraging at this stage of the model development (Figure 5). The model reproduces the base flow at the catchment outlet with a good order of magnitude (around 0.01 m3/s) and reacts to the rainfall events with a correct timing (although the  values  of  peak  discharges  are  still  approximative).  The  comparison  of  the  simulated discharge at point A and at the catchment outlet also shows that the water supply of the river reaches by the surrounding fields is effective thanks to the flow exchange interfaces. However the model fails to reproduce the seasonal variation of the discharge.First investigations showed that, although this seasonal variation is perceptible in the water table levels of the different agricultural fields (Figure 7), the computed lateral flows are not sensitive enough to the water table variations. Additional studies and tests are currently being undertaken to improve these aspects.Figure 5: Simulated and measured river discharges. Point A is located in the upper part of the catchment (see Figure 7).Figure 6: Simulation results for one of the tile-drained fields (see Figure 7 for the location of the field).ACatchment outletTile-drained fieldFigure 7: Simulated water levels for several agricultural fields and river reaches located at different places in the catchment.The outputs of the tile-drained zones (Figure 6) show fast reactions of the drained water table to the rainfall events. The two surface runoff peaks correspond to the most intense events.  These  results  are  consistent  with  what  can  be  observed  for  similar  sites  where measurements  are  available  (Branger  et  al,  2008).  The  tile-drained  zones  are  the  main contributors  to the catchment  fast  responses. The behaviour  of the hedgerows (results not presented here) is also consistent with our expectations: in the winter, the hedges have no influence on the water table dynamics and mainly a role of water transfer.              4. CONCLUSIONSThis  paper  presents  a  model  dedicated  to  the  assessment  of  the  influence  of  the influence  of  landscape  management  practices  on  the  hydrology  a  small  agricultural catchments.  This  model,  built  through  the  LIQUID  modelling  framework,  involves  four interconnected  modules  with  different  process  conceptualizations  for  the  relevant  hydro-landscapes in such watersheds. The first simulations conducted with this model show a good general functioning. In particular, the interfaces allow to calculate adequately flow exchanges between  the  modules.  The  results  are  physically  consistent,  in  spite  of  limitations  for simulating the seasonal variation of the discharge at the catchment outlet. The  next  step  in  the  model  tests  and  improvements  will  be  the  exploration  of parameter  sensitivities  and  the  setup  of  calibration  procedures  in  order  to  obtain  a  more accurate fit on the experimental data. Surface runoff will also be added in all the modules. This  will  allow  to  simulate  different  landscape  management  scenarios  and  to  assess  the influence of hedgerows and subsurface drainage on the hydrology of the Fontaine du Theil catchment.ACKNOWLEDGMENTSThe authors would like to thank Cemagref for funding of the LIQUID project and Arvalis/UIPP for providing the experimental data. Part of the work was also performed within the AVuPUR project funded by the French Agence Nationale de la Recherche (ANR).REFERENCESBranger, F. (2007), Using an environmental modelling framework for representing the influ-ence of landscape management practices on water quality. Application to the Fontaine du Theil experimental catchment (France), PhD Thesis, Grenoble, Université Joseph Fourier, 220 pp (in French).Branger, F., Tournebize, J., Carluer, N., Kao, C., Braud, I., Vauclin, M. (2008), A simplified modelling approach for pesticide transport in a tile-drained field: the PESTDRAIN model, submitted to Agricultural Water Management.Brooks, R. & Corey, A. (1964), Hydraulic properties of porous media, Technical Report, Col-orado State University.Dehotin, J., Braud, I. (2008), Which spatial discretization for distributed hydrological models? Proposition of a methodology and illustration for medium to large scale catchments, Hydrology and Earth System Sciences, 12, pp. 769-796.Miles, J. (1985), The representation of flows to partially penetrating rivers using groundwater flow models, Journal of Hydrology, 82, pp. 341-355.Ross, P. J. (2003), Modeling soil water and solute transport. Fast, simplified numerical solution, Agronomy Journal, 95(6), pp. 1352-1361.Viallet, P., Debionne, S., Braud, I., Dehotin, J., Haverkamp, R., Saadi, Z., Anquetin, S., Branger, F., Varado, N. (2006), Towards multi-scale integrated hydrological models using the LIQUID framework, 7th International Conference on Hydroinformatics, Nice, France, vol.1, pp 542-549.Viaud,  V.,  Durand, P.,  Merot,  P.,  Sauboua,  E.,  Saadi,  Z.  (2005),  Modeling the impact  of spatial structure of a hedge network on the hydrology of a small catchment in temperate climate, Agricultural Water Management, 74(2), pp. 135-163.

Modelling the Influence of Landscape Management Practices on the Hydrology of a Small Agricultural Catchment

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Modelling the Influence of Landscape Management Practices on the Hydrology of a Small Agricultural Catchment

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