Saturday, November 25, 2006

Measuring Unsaturated Hydraulic Flow

Developing a Dynamic Water Balance

Easy for laypeople and all sorts of experts to play or carry out experiments with an advanced hydrology long ignored on high technology for fluid applications to porosity at patenting affairs

In a simple approach using two lower-halves of disposable plastic bottles and a nylon cord it becomes easy to built a highly advanced self-watering pot as a soil-water-plant system that allows a constant measurement of Unsaturated Flow providing continuous parameters of Unsaturated Hydraulic Conductivity (mm/s). One lower half is set in the bottom as the water compartment. The other lower half is set in the top attached over the water deposit. The rooting media compartment on top should have two small holes in the bottom for a nylon cord insertion as an upsided 'U' having to hanging legs that reaches the bottom as a continuous flexible connection interface between water in the deposit and the rooting media porosity. This device can supply water constantly by Unsaturated Flow attending constant evaporative demands.

Unsaturated Hydraulic Conductivity is expressed as a volume of fluid (
mm3) crossing an area (mm2) by unit of time (s), simplified to mm3/mm2/s or simply mm/s. This figure below depict the spatial dynamics of continuous Unsaturated Flow from a point at the water table showing horizontal and vertical spread of water.

Like this figure above is showing It is reasonable to consider the fact that the flow of a fluid certainly can be observed in "real time" to quantify the detailed pattern structure of the motion. Consequently, mass motion involves measurements of time and distance. Simple experiments like this drying paper hanging in a wall can demonstrate spatially in less than an hour the attainable boundaries reachable by Unsaturated Hydraulic Flow. Water moves upward from a single point from the water table as a reference line offering a constant fluid supply from the Saturated Zone to attend a continuous demand throughout the Unsaturated Zone.

On the right this simple self-watering potted device is made of an ice-cream pot, When is sealed to prevent losses by evapotranspiration it can be used to provide a precise measurement of Unsaturated Hydraulic Conductivity. Water moves upward through a porous cord till reaching balance assessing its fluid conductibility when water is supplied constantly to attend unsaturated hydraulic gradients in the upper part. When the pot is open it provide results about variable Unsaturated Flow attending losses by evapotranspiration. This self-watering system in the picture registered (US pat. 6,766,817) the highest value of 2.18 mm/s of Unsaturated Hydraulic Conductivity which is many order times larger than reported by scientific literature. This happens because of molecular connectivity allowing a concentration of Unsaturated Hydraulic gradient to narrower pathways.

Experiments were carried out employing 2 kg of shadow dried soil which takes around 24 hours to achieve complete balance. For the highest Unsaturated Flow parameter the first 100 ml of water took just 27 minutes to move upward. Clayey soils achieved balance of unsaturation at about 44%, while sandy soils 33% and coarse sand 22% of water content v/v .

Developing a Dynamic Water Balance

An African Violet like in the left figure plant transpires around 24 ml of water per day. A water deposit of half liter (500 ml) is enough to supply luxurious water supply for root uptake to a single plant for around three weeks.

There is a common variation of water requirements by the plant depending on the plant size as well as weather conditions like temperature, wind velocity, and air humidity increasing or decreasing water losses by evapotranspiration accordingly.

Assuming that this plant on the left is consuming around 1.0 ml of water per hour that moves upward by two legs of 3 mm nylon cord.
Volume = 1.0 ml = 1.0 c
m3 = 1000 mm3
Area = 2 * π * r
2 = 2 * 3.14159 * 1.52 = 14.14 mm2
Time = 1 hour = 3600 seconds
Unsaturated Hydraulic Conductivity = 1000 m
m3 /14.14 mm2 /3600 s
Unsaturated Hydraulic Conductivity = 0.02 mm/s = 1.18 mm/min

The conductibility requirement of water transmission for this device above for African Violets is 110 times smaller than the maximum parameter achieved registering the value of 2.18 mm/s US pat. 6,766,817.


Henry Darcy proposed a Law about Saturated Hydraulic Flow in 1856 while Edgard Buckingham in 1907 suggest a modification for Unsaturated Hydraulic Flow. US pat. 6,766,817 is the first one to mention 'Unsaturated Hydraulic Flow' while 93,207 patents on capillary/capillarity/wick/wicking only 9 measured Unsaturated Hydraulic Conductivity. Today an advanced hydrology can provide an important technological edge for many industries delivering an enhanced hydrology like self-sustaining capability as shown by self-watering potted plants.

No comments: