Hydraulic characteristics and seepage modelling of clay pitchers produced in Jordan

摘要

The use of clay pitchers for irrigation is gaining considerable interest in arid and semi-arid lands due to its simplicity and auto-regulative capabilities. The saturated hydraulic conductivity, K_s, of pitchers is considered the most important factoraffecting the outflow rate from pitchers. The objectives of this study were to introduce a modified method of measuring K_s, survey hydraulic characteristics of locally produced pitchers, and develop a mathematical model that can predict seepage rate ofpitchers from the pitcher's geometry and production temperature before field installation. A modified falling head method and a constant head method were used to measure the saturated hydraulic conductivity of 14 pitchers selected from local producers in Jordan, with varying size, shape, and production temperature. The two methods of measuring K_s were found to be accurate. However, the procedure of the falling-head method was faster and simpler. The hydraulic conductivity of pitchers was found to range between 0.219 and 2.37 mm/d. The values of Ks tended to increase with production temperature. Surface sanding of the pitcher wall was found to increase the value of K_s by about 30%. The seepage rate from the pitchers to the atmosphere ranged from 600to 3700 mL/d, and was found to have a strong correlation with the pitcher's conductance. A mathematical conceptual model was developed to predict the seepage rates of pitchers from simple measurements and observations of the pitcher geometry. The model was first validated with measured conductance and other pitcher's properties in which the predicted seepage rate correlated very well with experimental data (R~2 = 0.97). The model prediction of seepage rate from the pitcher's volume, height, and predicted conductance, based on production temperature, was successful with R~2= 0.56 and an average absolute error of 23%. This latter model can be used to estimate the pitcher's seepage rate before field installation.