中国西北干旱区生态地下水埋深适宜深度的确定

干旱区影响天然植被生长的土壤水分和盐分,都和地下水埋深密切相关。地下水埋藏浅,在强烈的蒸发作用下,溶解于地下水中的盐分沿毛管上升水流于地表聚集,使土壤发生盐渍化,产生盐胁迫。地下水埋深过低,毛管上升水流不能到达植物根系层,植物生长受到水分胁迫,发生荒漠化。因此,确定既不会使土壤发生盐渍化和荒漠化的地下水埋深十分重要。本文根据地下水、土壤水及植物生长状况综合研究,把适宜的地下水埋深界定为在温带荒漠区1.5—4m,暖温带荒漠区2.0~4.0(4.5)m,即在潜水的强烈蒸发深度以下和蒸发极限深度之上的区间,为防治土地盐渍化、荒漠化和估算生态用水提供了科学依据。

Determination of Suitable Ecological Groundwater Depth in Arid Areas in Northwest Part of China

Soil moisture content and salt content affecting the growth of natural vegetations are closely related to groundwater depth in arid areas.Salts dissolved in groundwater can be carried upward by capillary water and accumulated in topsoil if groundwater depth is too shallow under the violent evaporation,thus,soil salinization and salt stress occur.Upward capillary water can not reach the rhizosphere of plants if groundwater depth is too deep,thus,the growth of vegetation is stressed by soil moisture,and land desertification occurs.Therefore,is it very important to determine suitable groundwater depth which does not result in soil salinization nor land desertification.According to the comprehensive study results of the situation of groundwater depth,soil moisture content and growth of vegetations,in this paper it is determined that the suitable groundwater depths should be 1.5~4.0 m and 2.0~4.0(4.5) m for the moderate deserts and the warm-moderate deserts respectively.That means the suitable groundwater depth should be in a range between the violent phreatic evaporation depth and the evaporation ultimate depth.The study results can provide the scientific basis for controlling soil salinization and land desertification and estimating water consumption for ecology.