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A geostatistical approach to the trickle irrigation design in heterogeneous soil: 1. Theory
Author(s) -
Russo David
Publication year - 1983
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/wr019i003p00632
Subject(s) - hydraulic conductivity , variogram , spatial variability , soil science , infiltration (hvac) , pressure head , drip irrigation , hydrology (agriculture) , spatial distribution , mathematics , soil water , environmental science , irrigation , physics , geotechnical engineering , geology , kriging , statistics , ecology , biology , thermodynamics
A geostatistical approach was used to investigate the spatial variability of two measured soil hydraulic parameters, the saturated hydraulic conductivity K s and α = d [log K(h) ]/[ d(h) ], where K is the hydraulic conductivity and h is the soil water pressure head. Using a linearized solution to steady infiltration from a circular shallow pond, the spatial distribution of the midway soil water pressure head between emitters, h c (for a given trickle discharge rate Q and spacing between emitters, d ), was calculated using the spatially variable soil parameters K s and α. The spatial distribution of the crop yield Y was calculated from the spatially variable h c by using a quadratic expression for the Y(h c ) relationships. It was found that the spatial variability of each of the measured input parameters ( K s and α) or the calculated output variables ( h c and Y ) is expressed through the variogram γ and can be characterized in terms of the coefficient of variation CV and the integral scale J . In the case of log K s , for which the sill is reached at relatively small range, two different γ were tested. Results showed that the kriged values of log K s as well as the resultant values of h c = h c (K s α; d, Q ) were relatively insensitive to the selected γ. The spatial variability of h c reduced the average (over the field) crop yield that would have been obtained when h c was uniform throughout the field. The spatially variable soil parameters K s and α were used to calculate the spatial distribution of the spacing between emitters (d) required to achieve (for a given trickle discharge) a prespecified value of h c , uniform throughout the field. It was found that the use of a spatially variable d increased the field crop yield by 3% relative to the yield that was obtained when a single‐valued d uniform throughout the field was used. The spatial distribution of d was combined with hydraulic principles to derive the spatial distribution of lateral diameter and length for engineering design requirements.