also in-situ methods for measuring the hydraulic conductivity in the field. When the water table is shallow, the augerhole method, a slug test, can be used for determining the hydraulic conductivity below the water table. The method was developed by Hooghoudt (1934) in The Netherlands and introduced in the US by Van Bavel en Kirkham (1948). The method uses the following steps: an augerhole is perforated into the soil to below the water table water is bailed out from the augerhole the rate of rise of the water level in the hole is recorded the -value is calculated from the data as: where: is the horizontal saturated hydraulic conductivity (m/day) is the depth of the water level in the hole relative to the water table in the soil (cm): at time at time is the time (in seconds) since the first measurement of as is a factor depending on the geometry of the hole: where: is the radius of the cylindrical hole (cm) is the average depth of the water level in the hole relative to the water table in the soil (cm), found as is the depth of the bottom of the hole relative to the water table in the soil (cm). The picture shows a large variation of -values measured with the augerhole method in an area of 100 ha. The ratio between the highest and lowest values is 25. The cumulative frequency distribution is lognormal and was made with the CumFreq program. Related magnitudes Transmissivity The transmissivity is a measure of how much water can be transmitted horizontally, such as to a pumping well. <small>Transmissivity should not be confused with the similar word transmittance used in optics, meaning the fraction of incident light that passes through a sample.</small> An aquifer may consist of soil layers. The transmissivity of a horizontal flow for the th soil layer with a saturated thickness and horizontal hydraulic conductivity is: Transmissivity is directly proportional to horizontal hydraulic conductivity and thickness . Expressing in m/day and in m, the transmissivity is found in units m2/day. The total transmissivity of the aquifer is the sum of every layer's transmissivity: The apparent horizontal hydraulic conductivity of the aquifer is: where , the total thickness of the aquifer, is the sum of each layer's individual thickness: The transmissivity of an aquifer can be determined from pumping tests.Influence of the water tableWhen a soil layer is above