Available Water Capacity for Australian Areas of Intensive Agriculture of Layer 1 (A-Horizon – Top-Soil)

\n\nSurface of predicted Available Soil Water Holding Capacity of layer 1 (A\nHorizon a Top-soil) surface for the intensive agricultural areas of Australia.\nData modelled from area based observations made by soil agencies both State\nand CSIRO and presented as 0.01 degree grid cells. Available water capacity\n(AWC) is a measure of the store of water available for plants to use. AWC is\npresented here as the estimated total for the horizon, measured in millimetres\n(mm). The amount of water that is held by the soil varies according to a\nnumber of soil properties including, soil texture, organic matter content,\nbulk density and soil structure development. Available water capacity has been\ncalculated as the difference in volumetric water content at 0.1 bar and 15 bar\n(matric potentials of -10 kPa and -1.5 mPa) for each layer. These represent\nrespectively the field capacity (maximum water content following free\ndrainage) and the permanent wilting point (lower limit of soil moisture\navailable to plants). The final ASRIS polygon attributed surfaces are a mosaic\nof all of the data obtained from various state and federal agencies. The\nsurfaces have been constructed with the best available soil survey information\navailable at the time. The surfaces also rely on a number of assumptions. One\nbeing that an area weighted mean is a good estimate of the soil attributes for\nthat polygon or map-unit. Another assumption made is that the look-up tables\nprovided by McKenzie et al. (2000), state and territories accurately depict\nthe soil attribute values for each soil type. The digital map data is provided\nin geographical coordinates based on the World Geodetic System 1984 (WGS84)\ndatum. This raster data set has a grid resolution of 0.001 degrees\n(approximately equivalent to 1.1 km). The data set is a product of the\nNational Land and Water Resources Audit (NLWRA) as a base dataset.\n\nSee [further metadata](http://data.daff.gov.au/anrdl/metadata_files/pa_awcaar9cl\n__06111a00.xml) for more detail.\n\n

澳大利亚集约农业区第一层（A层，即表层土壤）的预测有效土壤持水量（Available Soil Water Holding Capacity）空间表面数据。该数据基于各州土壤机构及联邦科学与工业研究组织（Commonwealth Scientific and Industrial Research Organisation, CSIRO）的区域观测数据建模生成，以0.01度的格网单元呈现。有效土壤持水量（Available Water Capacity, AWC）指可供植物利用的土壤储水量，本次数据中该指标为对应土层的估算总量，单位为毫米（mm）。土壤持水量受多种土壤属性影响，包括土壤质地、有机质含量、容重及土壤结构发育程度。有效土壤持水量通过各土层在0.1巴和15巴基质势下的体积含水量差值计算得到，对应的基质势分别为-10千帕（kPa）和-1.5毫帕（mPa）。二者分别代表田间持水量（自由排水后的最大含水量）与永久萎蔫点（植物可利用土壤水分的下限）。最终的澳大利亚土壤资源信息系统（Australian Soil Resource Information System, ASRIS）多边形属性表面数据，由各州及联邦机构获取的所有数据拼接镶嵌而成。该空间表面基于当时可获取的最优土壤调查信息构建，且依赖多项假设前提：其一，按面积加权的平均值可较好估算对应多边形或制图单元的土壤属性；其二，McKenzie等人（2000）及各州领地发布的查询表可准确反映各类土壤的属性数值。本数字地图数据采用基于1984世界大地测量系统（World Geodetic System 1984, WGS84）的地理坐标系，该栅格数据集的格网分辨率为0.001度（约合1.1千米）。本数据集为国家土地与水资源审计（National Land and Water Resources Audit, NLWRA）的基础数据集成果。详见[补充元数据](http://data.daff.gov.au/anrdl/metadata_files/pa_awcaar9cl__06111a00.xml)以获取更多细节。