Nutrient Transport Modelling in the Daugava River Basin - DiVA Portal

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moisture.Figure B1. Selection of curve number as a function of antecedentRecommended values of the break points AM1 and AM2 have been used (Dai et al,2000). The 5day antecedent precipitation is computed as follows:At=t∑ − 1n=t −5( Rn+ Mn)(B4)CN2 k values for different land uses are given in the BasinSim 1.0 User’s Guide (Dai etal, 2000).Values of CN1 k and CN3 k are computed from CN2 k :CN1kCN 2= k(B5)2.334 − 0,01334 ⋅ CN 2kCN3kCN 2= k(B6)0.4036 − 0.0059 ⋅ CN 2kAppendix C. Determination of potentialevapotranspirationPotential evapotranspiration is given by the following equation (Dai et al., 2001):PEt0.021⋅Ht⋅ et=T + 273t(C1)whereH t = number of daylight hours per day during the month containing day te t = saturated water vapour pressure on day t [mbar]T t = daily mean air temperature, average value for entire basin [°C]The saturated water vapour pressure is estimated from daily mean air temperature:32
8[( 0,00738⋅T+ 0.8072) − 0.000019( 1.8 ⋅T+ 48)+ 0.001316 ],T ≥ 0et= 33.8639ttt(C2)Appendix D. Determination of monthly sediment yieldThe monthly watershed sediment yield in the GWLF is determined from a model that isbased on three assumptions:(i)(ii)(iii)Sediment originates from sheet and rill erosion (gully andstream bank erosion are neglected)Sediment transport capacity is proportional to runoff to the5/3 powerSediment yields are produced from soil which erodes in thecurrent year (no carryover of sediment supply from one yearto the next)Accordingly, the sediment yield in a certain month will consist of contributions from allother months during that year. The contribution from each month will be equal to thesediment yield for that month multiplied by the fraction of total transport capacity inthat month (Dai et al., 2001).The total watershed sediment supply generated in month j is:Xj= DRj∑∑kdXkt(D1)t=1whereDR = watershed sediment delivery ratioX kt = erosion from land use k on day t [Mg]d j = number of days in month jErosion from land use k on day t is given by:Xkt= 0 .132 ⋅ RE ⋅ K ⋅ ( LS)⋅C⋅ P ⋅ AR(D2)tkkkkkwhereRE t = rainfall erosivity on day t [(MJ*mm)/(ha/h)]K k = soil erodibility factor(LS) k = topographic factorC k = cover and management factorP k = supporting practice factorThe product K*LS*C*P is called the erosion factor. Standard values for K, C and P fordifferent land uses and soil types can be found in tables in the BasinSim User’s Guide(Dai et al., 2000). LS is determined from data on topography. Rainfall erosivity isestimated by the following empirical equation:RE1.81t= 64.6⋅ at⋅ Rt(D3)33
Page 1 and 2: UPTEC W05 009Examensarbete 20 pFebr
Page 3 and 4: Nyckelord: avrinning, näringsämne
Page 6 and 7: APPENDIX C. DETERMINATION OF POTENT
Page 8 and 9: simulation system CatchmentSim. The
Page 10 and 11: Figure 1. The hydrological part of
Page 12 and 13: TemperaturePrecipitation20.00120deg
Page 14 and 15: 3.2 MODEL DESCRIPTION3.2.1 An overv
Page 16 and 17: Groundwater discharge to the river
Page 18 and 19: Groundwater nutrient loadsThe groun
Page 20 and 21: There is therefore no guarantee tha
Page 22 and 23: a) Streamflow, calibration periodb)
Page 24 and 25: 4.2 IMPACT OF THE CURVE NUMBER ON N
Page 26 and 27: the chosen value is a very rough ap
Page 28 and 29: all cultivated land will have winte
Page 30 and 31: HELCOM, 2004a. 30 years of protecti
Page 32 and 33: Appendix A. Input data and paramete
Page 34 and 35: Description of parameter/input Name
Page 36 and 37: Description of parameter/input Name
Page 40 and 41: wherea t = rainfall erosivity coeff
Page 42 and 43: Appendix F. Regression lines of rep

Nutrient Transport Modelling in the Daugava River Basin - DiVA Portal

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