Review: The auto-regulative capability of pitcher irrigation system (Abu-Zreig et alii, 2006)

Table of Contents

Objective of the study
Description of the experiments



Title: The auto-regulative capability of pitcher irrigation system
Authors: Abu-Zreig, Majed M., Abe, Yukuo, Isoda, Hiroko
Type of Study: Experimental laboratory study
Journal: Agricultural Water Management, vol. 85, 2006, 272-278.
Open Access: No. 35,95 USD.


Objective of the study

“The objective of this study is to quantify the response of pitcher’s seepage rate to potential evaporation using a systematic laboratory study.” [273]



Type of experiment: Lab study
Country: Japan
Place: not given
Timespan: not given, based on the graphics it seems about 11-12 days
Soil Type:
Number of pitchers: 4
Parameters analysed Seepage rate, pan evaporation rates



1. Introduction

2. Materials and methods

3. Results and discussion

4. Conclusions



Description of the experiment

Pitcher characteristics

Pitcher Volume (ml) Height (cm) Average wall thickness (cm) Maximum outside diameter (cm) Base diameter (cm) Surface area (mm2 x 10-2) Hydraulic conductivitya) (mm/d)
Conductance (mm2/d x 10-2)b) Saturated water content, w (%) Porosity (%)
A1 5016 30 8.1 20 10 1443 1.040 185.3 21.1 32.9
A2 5365 29.5 7.9 21.5 10.3 1496 0.963 182.4 20.9 31
B1 4624 29 7.7 20.4 10.2 1377 0.116 20.7 16.9 26.5
B2 4909 29.3 8.1 21.4 10.2 1420 0.120 21 16 25

a) at saturation measured by the falling head method
b) Conductance equal to (Ks  surface area)/wall thickness of pitcher

The four clay pots in this experiment were manufactured at the Kasama Institute, Japan.

“Two of the pitchers have light green colour and the other two have red brown surface colour indicating a difference in the manufacturing materials. The green pitchers were described qualitatively by the manufacturer as having high porosity whereas the brown ones were characterized as low-porosity pitchers.” [274]

Soil characteristics

Experimental Set-up

“All experiments lasted for about 150–300 h depending on the pitcher seepage rate.” [275]

“The seepage rate of pitchers was measured in a closed chamber under controlled temperature and humidity. Pitchers were filled with water, placed inside the chamberand the loss in their weight was record edevery 12 h for at least 1 week. Pitchers were refilled on the second day only, when pitchers had reached equilibrium with the surrounding environment, and then left for seepage under variable head condition until the end of the experiment.” [275]

“Six sets of experiments were conducted named as room, Rh100, T20, T30, T40 and T45. The ‘‘room’’ set refers to the experiments conducted at room temperature and humidity; Rh100 were experiments for controlled conditions at about 97% relative humidity and 20 8C; T20, T30, T40 and T45 were controlled experiments at temperatures of 20, 30, 40 and 45 °C, respectively; The humidity for these later experimentswas kept at 60% except in the case of 45° in which humidity was about 40% to provide conditions of increased potential evaporation from the combination of low humidity and high temperature.” [275]

“A water container was placed in the chamber for each experiment to measure pan evaporation (Ep) at the prevailing conditions.” [275]

“The temperature and humidity inside the chamber were varied to quantify the influence of evaporation potential on pitcher’s seepage rate.” [275]

“Small variations inthe pan evaporation rates did occur because it was not possible to completely control the inside temperature and humidity in the chamber as shown in Fig. 4.” [275]

“To further analyse the relative influence of the depth of water in the pitchers and the potential evaporation, the seepage rate is plotted against the seepage volume as a percentage of pitcher’s volume for the T20 and T40 experiments and the results are shown in Fig. 7.” [276]

“For further analysis, the influence of climatic factors on seepage rate a correlation between pitcher’s seepage rate and pan evaporation for the two types of pitchers A and B was performed (…)” [276]



“High porosity type A pitchers had slightly higher seepage compared to type B for both experiments. Seepage differences between the two types of pitcherswere also larger during the first 48 h of the experiment” [275]

“seepage volume increased with experimental temperature and increased linearly with time for both types of pitchers, indicating a relatively constant seepage rate with time.”  [275]

“Type B pitchers required longer adjustment time to the surrounding environment compared
to type A pitchers especially for experiments with high temperatures as in T40 experiment.”

“Once the pitcher is in equilibriumwith its environment, the seepage rate is affected by the pressure head determined by the depth of water inside the pitcher and the pressure head distribution on the outside pitcher surface due to evaporation. [276]

The influence of evaporation on seepage rate was more important than that of water depth inside the pitcher.” [276]

“The decrease in pitcher seepage seemed negligible until seepage volume reached about 60–70% of the pitcher volume. At that point, pitchers should be refilled with water to maintain seepage rate and therefore soil water level at favourable conditions for plant growth. Other researchers have also indicated that pitchers should be refilled with water when pitchers loose about 50% of their volume (Daka, 1991).” [276]

“For further analysis, the influence of pressure head on pitcher’s seepage rate was much larger than that of its hydraulic conductivity or conductance, the factor that accounts for the combined effect of hydraulic conductivity, surface area and wall thickness of pitchers (…) The figures show a linear and positive relationship between seepage rate and Ep.” [277]

“These results indicted the strong auto-regulative capability of clay pitchers. It is clear that the influence of pressure head distribution on the outer surface of clay pitchers is greater than that of the pressure head distribution induced by the water depth inside pitchers.” [277]



“Results from controlled pitcher experiments showed quantitatively for the first time that clay pots have strong auto-regulative capability.” [277]

“A strong linear relationship was found between pan evaporation and seepage rates of clay pitchers.” [277]

“The seepage rates of type A pitchers, characterized by high porosity and hydraulic conductivity, increased from 190mL/d to as high as 1040 mL/d when Ep increased from1 to 16mm/d. The corresponding increase for type B pitchers, characterized by low porosity and hydraulic conductivity, was from 60 to 1000 mL/d.” [277]

“The influence of pitcher’s hydraulic properties on seepage rate seemed to be strong at low Ep values but weak at high Ep values.” [277]

“These results indicated that most types of clay pitchers can be suitable for irrigation under arid climates having high potential evaporation.” [277]



In preparation

If you are interested in ancient and traditional technologies and their modern day applications, take a look at my other websites:

The Amatek Institute – Ancient Technologies in Modern Contexts

My Blog about ancient and traditional sustainable technologies and their modern day applications