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THIRD MEETING SADMO LISBON, PORTUGAL, 7 SEPTEMBER 2007

THIRD MEETING SADMO LISBON, PORTUGAL, 7 SEPTEMBER 2007. -- WATER RESOURCES INDICATORS AND STATISTICAL ANALYSIS OF THE HYDROLOGICAL DATA EAST OF GUADIANA RIVER AT REGIONAL SCALE - REGIONAL HYDROLOGY AND SOIL EROSION IN THE PILOT BASIN EAST OF GUADIANA RIVER, PORTUGAL

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THIRD MEETING SADMO LISBON, PORTUGAL, 7 SEPTEMBER 2007

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  1. THIRD MEETING SADMOLISBON, PORTUGAL, 7 SEPTEMBER 2007 --WATER RESOURCES INDICATORS AND STATISTICAL ANALYSIS OF THE HYDROLOGICAL DATA EAST OFGUADIANA RIVER AT REGIONAL SCALE - REGIONAL HYDROLOGY AND SOIL EROSION IN THE PILOT BASIN EAST OF GUADIANA RIVER, PORTUGAL V. HRISSANTHOU, K. ILIOPOULOS, S. CHARITOPOULOS, P. ANGELIDIS AND N. KOTSOVINOS DEPARTMENT OF CIVIL ENGINEERING DEMOCRITUS UNIVERSITY OF THRACE 67100 XANTHI, GREECE

  2. DUTH RESEARCH OBJECTIVES • REGIONAL STATISTICAL – HYDROLOGIC ANALYSIS OF THE PRECIPITATION DATA • WATER RESOURCES INDICATORS AT REGIONAL SCALES AND VARIOUS TIME SCALES • TEST FOR THE APPROPRIATE PROBABILITY DENSITY DISTRIBUTION TO DERIVE THE STANDARDIZED PRECIPITATION INDEX (SPI) AT REGIONAL SCALE FOR VARIOUS TIME SCALES; KOLMOGOROV-SMIRNOV GOODNESS-OF-FIT TEST; TEST FOR THE QUANTITY OF DATA

  3. STANDARDIZED PRECIPITATION INDEX (SPI) FOR VARIOUS TIME SCALES AT MANY STATIONS COVERING THE REGION UNDER STUDY, USING THREE DIFFERENT PROBABILITY DENSITY DISTRIBUTIONS; TREND OF SPI DUE TO CLIMATIC CHANGES. • REGIONAL STATISTICAL ANALYSIS OF TEMPERATURE AND EVAPORATION . • ADDITIONAL DROUGHT INDICATORS COMBINING HYDROLOGIC , EVAPOTRANSPIRATION AND VEGETATION DATA. • BASIC RESULTS ARE INCLUDED IN OUR REPORT. • IN THIS PRESENTATION, WE PRESENT THE INTERCONECTION BETWEEN HYDROLOGY AND SOIL EROSION .

  4. INTRODUCTION • Computation of soil erosion in the pilot basin east of Guadiana River to Portugal-Spain border (2853 km²) • Division of the pilot basin into 136 sub-basins by means of a quadrangular grid (5 km x 5 km) • Application of the Universal Soil Loss Equation (USLE) • Construction of the isoerodent map for the pilot basin

  5. UNIVERSAL SOIL LOSS EQUATION (USLE) A = R K LS C P A: mean annual soil loss per unit area (t/ha) R: rainfall erosivity factor (N/h) K: soil erodibility factor [(t/ha) / (N/h)] LS: topographic factor C: soil cover factor (cropping management factor) P: erosion control practice factor

  6. AVAILABLE DATA Monthly rainfall data from the following 14 stations: (time period of data, mean annual rainfall amount) • Aldeia Nova de sto Bento (1932 – 1972) (575.45 mm) • Amareleja (1932 – 2006) (530.74 mm) • Amieira (1952 – 2000) (579.74 mm) • Barrancos (1932 – 2002) (557.49 mm) • Herdade da Valada (1969 – 2006) (510.59 mm) • Mesquita (1981 – 2006) (472.79 mm) • Mirtola (1932 – 2000) (433.01 mm) • Minas de sto Domingos (1932 – 1967) (433.01 mm)

  7. AVAILABLE DATA • Pedrogto do Alentejo (1942 – 2006) (518.80 mm) • Reguengos (1932 – 2006) (555.61 mm) • Santa Iria (1981 – 2006) (460.34) • Santo Aleixo da Restaurahto (1932 – 2006) (491.96 mm) • Serpa (1932 – 2006) (528.31 mm) • Sobral da Adiha (1981 – 2006) (526.69 mm)

  8. Meteorological stations in the area under study (Guadiana)

  9. AVAILABLE MAPS • Digitized maps: - Square grid map (constructed) - Contours map (maximum altitude 580 m) - Thiessen polygons map (constructed)

  10. SQUARE GRID MAP

  11. CONTOURS MAP

  12. THIESSEN POLYGONS MAP

  13. ESTIMATION OF THE RAINFALL EROSIVITY FACTOR (R) • Rainfall erosivity factor (R) for a rainfall event: Product of two rainstorm characteristics, kinetic energy and the maximum 30 minute intensity • A continuous record of rainfall intensity is required • Empirical regression equation for the rainfall erosivity factor (Schwertmann et al., 1990): R = 0.083N-1.77 R: rainfall erosivity factor (N/h) N: mean annual rainfall amount (mm)

  14. ESTIMATION OF THESOIL ERODIBILITY FACTOR (K) The value of K depends on the soil characteristics (% sand, % silt + very fine sand, % organic matter, structure, permeability) An average value for the whole basin was estimated approximately: K = 0.28 (Lithosols, diagrams in Mitchell and Bubenzer, 1980)

  15. ESTIMATION OF THE TOPOGRAPHICAL FACTOR (LS) LS = (λ/22.13)m (0.065+0.045s+0.0065s²) (see Mitchell and Bubenzer, 1980) LS: topographical factor λ: slope length (m) s: slope gradient (%) m: exponent depending on the slope gradient For slope gradients greater than 30% (van Vuuren, 1982): LS = (λ/22.13)m 16 [sin2(arctan(s/100))]1.6

  16. ESTIMATION OF THE TOPOGRAPHICAL FACTOR (LS) Computation of the slope gradient s (Williams and Berndt, 1972): si = [H(Lj+Lj+1)/2Fi] x 100 si: slope gradient(%) of the area i between the contours j and j+1 H: altitude difference between the contours j and j+1 Lj, Lj+1: length of the contours j and j+1, respectively Fi: size of the area i

  17. ESTIMATION OF THE TOPOGRAPHICAL FACTOR (LS) n s = (Σ siFi)/F i=1 s: mean slope gradient of a sub-basin F: sub-basin area n: number of the areas between contours in a sub-basin λ = 150 m (Huggins and Burney, 1982)

  18. ESTIMATION OF THESOIL COVER FACTOR (C) Soil cover percentage for the whole basin: forest 15.96%, bush 19.46%, urban area 3.07%, no vegetation 19.0% fruit-trees 32.24%, irrigated land 1.45%, meadow 2.98% Cforest = 0.004 Cbush = 0.03 (Wischmeier and Smith, 1978) Curban area = 0.001 Cno vegetation = 0.20 (Schwertmann et al., 1990) Cfruit-tree = 0.09 Cirrigated land = 0.18 Cmeadow = 0.10

  19. ESTIMATION OF THE SOIL COVER FACTOR (C) Csub-basin = CforestFforest + CbushFbush + CurbanFurban + Cno veget.Fno veget. + + Cfruit-treeFfruit-tree + Cirrig. landFirrig. land + CmeadowFmeadow Fforest: percentage of forest in the sub-basin considered Fbush: percentage of bush in the sub-basin Furban: percentage of urban area in the sub-basin Fno veget.: percentage of area with no significant vegetation Ffruit-tree: percentage of fruit-trees in the sub-basin considered Fmeadow: percentage of meadow in the sub-basin considered

  20. ESTIMATION OF THEEROSION CONTROL PRACTICE FACTOR (P) P = 1.0 Most unfavourable case: no erosion control practices were applied to the basin

  21. ARITHMETIC RESULTS FOR SOIL EROSION • The mean annual soil loss in the sub-basins varies from 0.50 to 18 t/ha or from 50 to 1800 t/km² • The mean annual soil loss in the whole basin (2853 km²) amounts to approximately one million tons or 3.78 t/ha or 378 t/km²

  22. ISOERODENT MAP

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