Abstract The implementation of site-specific land drainage system designs is usually disregarded by landowners in favour of locally established ‘standard practice’ land drainage designs. This is due to a number of factors such as a limited understanding of soil–water interactions, lack of facilities for the measurement of soil’s physical or hydrological parameters and perceived time wastage and high costs. Hence there is a need for a site-specific drainage system design methodology that does not rely on inaccessible, time-consuming and/or expensive measurements of soil physical or hydrological properties. This requires a standardised process for deciphering the drainage characteristics of a given soil in the field. As an initial step, a new visual soil assessment method, referred to as visual drainage assessment (VDA), is presented whereby an approximation of the permeability of specific soil horizons is made using seven indicators (water seepage, pan layers, texture, porosity, consistence, stone content and root development) to provide a basis for the design of a site-specific drainage system. Across six poorly drained sites (1.3 ha to 2.6 ha in size) in south-west Ireland a VDA-based design was compared with (i) an ideal design (utilising soil physical measurements to elucidate soil hydraulic parameters) and (ii) a standard design (0.8 m deep drains at a 15 m spacing) by model estimate of water table control and rainfall recharge/drain discharge capacity. The VDA method, unlike standard design equivalents, provided a good approximation of an ideal (from measured hydrological properties) design and prescribed an equivalent land drainage system in the field. Mean modelled rainfall recharge/drain discharge capacity for the VDA (13.3 mm/day) and ideal (12.0 mm/day) designs were significantly higher (P < 0.001, s.e. 1.42 mm/day) than for the standard designs (0.5 mm/day), when assuming a design minimum water table depth of 0.45 m.

中文翻译：

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视觉排水评估：用于爱尔兰土地排水设计的标准化视觉土壤评估方法

摘要 土地所有者通常会忽视特定地点土地排水系统设计的实施，转而采用当地建立的“标准做法”土地排水设计。这是由于许多因素造成的，例如对土壤-水相互作用的了解有限、缺乏测量土壤物理或水文参数的设施以及感知到的时间浪费和高成本。因此，需要一种不依赖于难以接近、耗时和/或昂贵的土壤物理或水文特性测量的场地特定排水系统设计方法。这需要一个标准化的过程来破译给定土壤在田间的排水特性。作为第一步，一种新的可视化土壤评估方法，称为可视化排水评估 (VDA)，介绍了使用七个指标（渗水、盘层、质地、孔隙度、稠度、石头含量和根部发育）近似特定土壤层的渗透性，为特定场地排水系统的设计提供基础. 在爱尔兰西南部的六个排水不良的场地（面积为 1.3 公顷至 2.6 公顷）中，基于 VDA 的设计与 (i) 理想设计（利用土壤物理测量来阐明土壤水力参数）和 (ii) 标准设计进行了比较通过地下水位控制和降雨补给/排水能力的模型估计设计（0.8 m 深的排水沟，间距为 15 m）。与标准设计等效方法不同，VDA 方法提供了理想（来自测量的水文特性）设计的良好近似，并规定了现场等效的土地排水系统。