Menyanthes User Manual - KWR Watercycle Research Institute

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7.1.1 Options in the Groundwater Level Series frameTo the left in this frame, you can find a listbox with the names of the series that are beingmodelled. The Observation interval (obs. interval) shows the median time step of theobservations of the selected series. Next to the listbox are two options that affect the modellingprocess:1) Sample groundwater level series: When this box is checked the groundwater levelseries will be resampled on the same frequency as the explanatory series (which can bespecified in the explanatory series frame, see also section 7.1.2). This option reduces thecalculation time, but can lower the accuracy.2) Non-linear: When this box is checked, a time series model with threshold non-linearityis estimated. Note that non-linear time series models can only deal with precipitationand evaporation as explanatory series. For more information on this topic, see [VonAsmuth et al., 2006].Note: when selecting one of the above options, it will be applied to the groundwater levelseries (one or more) currently selected in the listbox.7.1.2 Options in the Explanatory Series frameThe listbox in this frame shows the explanatory series that will be included in the time seriesmodel for the selected groundwater level series. The observation interval (obs. interval)indicates the median time step of the selected explanatory series. A number of options areavailable for each explanatory series:1) IR function: Selects the type of impulse response function used for this series. Theoptions are: Precipitation (PREC), Evaporation (EVAP), Pumping (WELL), Surfacewater levels (RIVER), instantaneous effect (IMPULSE), and Box-Jenkins ARMA function(BOXJEN).2) Sample frequency: Select the frequency to which the explanatory series are sampledand/or interpolated.3) Interpolate: Select this option to make the explanatory series equidistant by linearinterpolation.4) Model order (only for Box-Jenkins models): Select the number of moving averageparameters that will be estimated.These options affect the calculation time and way in which the response of the system ismodelled. By default, options 2) and 3) are ‘weekly resampling’ and ‘interpolate’. A weeklyfrequency generally yields good results, except for very fast systems. When you have enteredthe type of the explanatory series correctly at the import procedure, Menyanthes willautomatically select the correct default response function for each series.7.1.3 Adding explanatory seriesThe three buttons next to the Explanatory Series listbox allow you to view a series, add a seriesor delete a series. When the add button is clicked, a pop-up appears (Figure 12). From thelistbox select the series to be added and click OK. When adding a linear or step trend, you haveto specify the period or date of the change in a separate pop-up( Figure 11).Menyanthes Manual© KWR - 27 -
Figure 11: For step trends enter the date of the changein the edit box and click OKFigure 12: Select explanatory series in the listbox and click OK to add them to the model.7.2 Initial condition and start-upperiodIt is important to take intoaccount the effect of theexplanatory series prior to thefirst groundwater levelobservation. After all, the firstgroundwater level observation isthe resultant of everything thathas happened in the precedingperiod with regard toprecipitation, evaporation,pumping etc. One has todistinguish the:h( t)p ( t)pinitial conditionstart-up periodAutomatically Data /max 8 yeartimeCalbration periodOverlapFigure 13: The role of the initial condition, the start-upand calibration period.a. Start-up period – The period prior to the first groundwater level observation for whichdata on the explanatory series is available.b. Initial condition – The average value of the explanatory series from minus infinity untilthe first explanatory series data.Ideally, the length of the start-up period is as long as the memory of the groundwater system.However, the longer the start-up period, the more data needs to be processed so the longer thecalculation time will be. To reduce calculation time, Menyanthes shortens explanatory series asfollows:1) The latest start date among the explanatory series is used and the values of the otherexplanatory series before this date are ignored.Menyanthes Manual© KWR - 28 -
Page 2 and 3: Menyanthes User ManualVersion 2.x.b
Page 4 and 5: ContentsContents 11 Introduction 41
Page 6 and 7: 10 List of references 47I Appendix
Page 8 and 9: - Improved output at different scre
Page 10 and 11: 2 Technical specifications andrequi
Page 12 and 13: 3 The installation procedure3.1 Ins
Page 14 and 15: Since then, Menyanthes also require
Page 16 and 17: New - open a new databaseOpen - fin
Page 18 and 19: 4.5 The ‘Explanatory Series’ se
Page 20 and 21: 5 Database and graphic functionalit
Page 22 and 23: pumping well or other explanatory s
Page 24 and 25: Figure 8 Module for editing the tec
Page 26 and 27: 6 Groundwater statistics6.1 The sta
Page 28 and 29: • Simulated series are affected b
Page 32 and 33: 2) Values of the explanatory series
Page 34 and 35: plotted, together with the estimate
Page 36 and 37: 8 Simulating groundwater level seri
Page 39 and 40: Figure 22 the two tabs of the Spati
Page 41 and 42: 1. Enter the barametric datalogger
Page 43 and 44: The three section of the Diver Data
Page 45 and 46: Figure 25 Screen to get a detailed
Page 47 and 48: Figure 26 The edit screen for datal
Page 49 and 50: Figure 27 Screen to edit technical
Page 51 and 52: I Appendix A: Description of import
Page 53 and 54: length of the sediment sump of the
Page 55 and 56: 2. Go the menu and to Tools > Digit
Page 57 and 58: M0 PRECSDEVEVAP FWELL NAMEM0 WELL-
Page 59 and 60: IV Appendix D: Data structure in MA
Page 61 and 62: V Appendix E : AcknowledgementsFina
Page 63: Postbus 1072 3430 BB Nieuwegein The

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