Saline wetlands related to groundwater flows from low permeability Tertiary formations in the Somontano area of Huesca,Spain

Presence of groundwater flow in the ‘Somontano de Huesca’ Area, derived from low‐permeability detrital Tertiary rocks, is considered. A groundwater flow model is constructed for these Tertiary rocks. This model explains both water flow through them and the chemical characteristics of the water. Groundwater flow has clear surface manifestations: it causes wetlands (which are called ‘paules’ in the area) with sodic waters, it produces saline, sodic or alkaline soils, and it produces modifies the chemical composition of rivers in Somontano. Irrigation has increased the volume of filtered water, especially in the interfluve areas, causing the extension of the wetlands in the valley thalwegs, and also the greater movement of salts has increased the problems of saline and/or sodic soils in the area. Copyright © 2001 John Wiley & Sons, Ltd.