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1 Hydrogeomorphic Pothole Types in Agricultural Landscapes of East- Brandenburg Centre for Agricultural Landscape and Land Use Research (ZALF) Thomas Kalettka ZALF, Institute of Hydrology, tkalettka@zalf.de Slide 2 2 Agricultural landscape with potholes in spring Slide 3 3 Soll (German); pothole, kettle hole (English) = glacially shaped isolated depression within the sink of an internal catchment in the young moraine landscape standing water or wetland respectively - water areaSlide 4 4 Slide 5 5 Water regime of potholes in agricultural landscapes of East-Brandenburg Mapping of wetness 1993-2002 Slide 6 6 Morphological parameters of a pothole Cross section Top view EB = Edge border TSB = Top shore border BSB = Bottom shore border HwL = High water line MwL = Middel water line Slide 7 7 Classification of hydrogeomorphic variables of potholes VariablesClasses 12345 catchment area [ha] 1.0 very small 3.2 small 10.0 middle 31.6 big > 31.6 very big area ratio 3 very small 10 small 32 middle 100 big > 10 very big catchment reliefflatslightly rollingmiddle rollingstrong rollinghilly pothole area [ha] 0.03 very small 0.10 small 0.32 middle 1.00 big > 1.00 very big maxiumum depth bottom shore depth [m] 1.0 very wadeable 1.6 wadeable 2.5 very shallow 4.0 shallow > 4.0 deep shore slope [%] 10 flat 20 sloping 30 very sloping 40 steep > 40 very steep shore width [m] 4 very narrow 6 narrow 10 middle 16 wide > 16 very wide length/width at top shoreline 1.5 roundish 2.5 oval > 2.5 stretched water regimenever watertemporary (episodic) seasonally (periodic) semiper- manent permanent shore overflow tendency notpartlycompletely Slide 8 8 Factor analysis of hydrogeomorphic variables of potholes (n=144) VariablesCatchment and Pothole Area Factor Overflow Factor Relief and Shape Factor water regime 0.86 0.13-0.12 shore overflow tendency -0.06 0.85 0.07 catchment area 0.65 0.19-0.27 catchment relief 0.18 -0.05 -0.76 pothole area 0.81 0.24-0.24 maximum depth 0.75 -0.430.07 max. depth bottom shore depth 0.81 -0.140.03 length/width 0.030.08 -0.77 shore slope -0.16 -0.86 0.11 explained variance (value)3.101.801.36 part of total variance %342015 extraction: main components; factor rotation: varimax; results: factor loadings of variables, marked loadings 0,65 Slide 9 9 Cluster analysis for derivation of hydrogeomorphic pothole types Example: Cluster of shallow potholes (n=95, mean values, K-Means-Cluster analysis) WR = Water regime; SBT = Shore overflow tendency, CA = Catchment area; PA = Pothole area at top shore; SS = Shore slope Slide 10 10 potholes (isolated depressions with vertical water fluctuation) 2. Water bearing Types (permanent to temporary flooded, organic and mineral sediments) WR: 2-5 1. Fen-Type (growing fen) WR: 1-2 2.1 Storage-Type (permanent shore) WR: 2-5 2.2 Shore Overflow-Type (permanent shore) WR: 2-5 2.3 Puddle Type (nonpermanent shore) WR: 2 2.1.1 Big Deep WR: 4-5 2.1.2. Big Shallow WR: 3-5 2.1.3 Small Shallow WR: 2-3 2.1.4 Small Wadeable WR: 2-3 2.2.1a Big Shallow WR: 3-5 2.2.2 Big Wadeable WR: 3-5 2.2.3 Small Shallow WR: 2-4 2.2.4 Small Wadeable WR: 2-3 2.2.1b with peaty island WR: 3-5 WR = Water Regime 1: never, 2: episodic (temporary, 3: periodic (seasonal), 4: semipermanent, 5: permanent Hydrogeomorphic types of potholes in agricultural landscapes Slide 11 11 Short form of the determination key for water bearing hydrogeomorphic pothole types 1.2.3.4. Pothole TypeMDPermanent shore SSOTPACAWRCR never