Hydropedological Data Necessary for Computing Drain Spacings in a Gleysol

Abstract

Gleysols comprise soils saturated with groundwater for long enough periods to develop reducing conditions resulting in gleyic properties. Gleysols occupy more than 720 million ha worldwide, on low positions in landscapes with high groundwater table. Evidence of reduction processes with segregation of Fe compounds starting in the first 40 cm of the soil surface. For many gleysols the main obstacle to utilization is the necessity to install a drainage system to lower the groundwater table. With a particle – size distribution clayey – loamy (44.8-42.9% clay), a great bulk density (1.50-1.57g/cm3), and SAR 12.5, these soils have a poorly natural drainage, from which water is removed very slowly. The volume of all pores, namely porosity, is very small in the second horizon, 38.3%. The primary function of a drainage equation is the computation of drain spacings for drainage design. An analysis reveals the influence of the various factors, as permeability, thickness of the soil layers, depth of drains, discharge rate in surface, effective porosity, drainage intensity etc; namely geohydrological investigations. In order to determine the drain spacing on the Gleysols we have used a similar method with the auger-hole method (1970, van Beers) but with 4 holes. The water was removing from the central auger-hole with a bailer, the time interval was 20 minutes. The analytical data of measurements are in the tables 2 and 3. Knowing the pumped and extracted water volumes from central auger hole which has perforated tube, we have obtained the final values of effective (or drained) porosity (0.0197-0.0208). For the drain space calculation, we recommend to use 0.0208, the finally value.