Depth to water - simulated 1970 steady state raster

## **Abstract** \n\nThis dataset and its metadata statement were supplied to the Bioregional Assessment Programme by a third party and are presented here as originally supplied. \n\n\n\nThe simulated 1970 unconfined depth to watertable across the entire model domain. This represents a pre-development water table surface. \n\n\n\nChoosing a year that best represents the climatic circumstances for the simulation objectives is an essential part of the steady-state assessment. This decision was influenced by the availability of appropriate calibration data. This approach generally allows for the selection of a year that was outside the bounds of a longer term shift in annual rainfall distribution. The selected steady-state condition was based on 1970 rainfall and assumed no groundwater extractions. This initial state was selected to represent predevelopment conditions as post-1970 historic groundwater pumping in the region (on and offshore) have not achieved a quasi-equilibrium response as based on available groundwater hydrograph trends. \n\nThe transient simulation period was 1970 to 2012. This period captures both pre-mine development and a range of varying climatic conditions, including above average wet and dry sequences. The 1970 starting date enables the incorporation of historic groundwater extraction data into the model and provides sufficient lead time for the groundwater model to minimise the impact of initial conditions on model predictions associated with the period of interest, namely the calibration/validation period of 2000 to 2012. \n\n\n\nCopied from the Gippsland Groundwater Model report, 2015.\n\n## **Purpose** \n\nThe steady-state calibration model represents the 1970 Latrobe Valley pre-development conditions. On the basis that steady-state predictions reflect long-term equilibrium conditions assuming constant groundwater inputs and stresses throughout time, no groundwater extractions were assigned during the steady-state simulation.\n\n## **Dataset History** \n\n"The simulated 1970 unconfined potentiometric surface (watertable) and depth-to-watertable across the entire model domain is shown in Figure 114 and Figure 115 respectively. (ED. see figures in the Gippsland Groundwater model report)\n\nVisual comparison of the Victorian SAFE depth to watertable map (Figure 116) with the steady-state simulated depth to watertable shows the watertable surface is reasonable within the alluvial systems, however in some upland locations the watertable appears in greater connection with surface features than presented in the Victorian Aquifer Framework (VAF) data. This is not considered a significant issue as these areas are well beyond the zone of interest.\n\nIt must be noted that the VAF depth to watertable map was derived using a combination of terrain analysis and interpolated bore data, and in part on proximity to streams within the exposed basement areas. Additionally, the VAF reflects the 1990 conditions whereas the simulated steady-state depth to watertable represents pre-development conditions. As such, it is expected that that the simulated steady-state depth to watertable map would have a greater area of shallow watertable than reported in the VAF spatial layer."\n\n\n\nThis text copied from the Gippsland Groundwater Model report 2015.\n\n## **Dataset Citation** \n\nVictorian Department of Economic Development, Jobs, Transport and Resources (2015) Depth to water - simulated 1970 steady state raster. Bioregional Assessment Source Dataset. Viewed 05 October 2018, http://data.bioregionalassessments.gov.au/dataset/4f343452-3dae-4184-b5f5-5690a17a82f6.

**摘要**

本数据集及其元数据声明由第三方提供给生物区域评估计划（Bioregional Assessment Programme），并按原始提交形式在此呈现。

模拟得到的1970年全模型域非承压地下水位埋深（unconfined depth to watertable），代表开发前的地下水面。

选取最契合模拟目标气候条件的年份，是稳态评估的关键环节。该决策受限于合适率定数据的可获得性，该方法通常可选取处于长期年降雨分布变化范围之外的年份。本次选定的稳态条件基于1970年的降雨数据，并假设无地下水开采。选取该初始状态以代表开发前条件，原因是该区域1970年后的历史地下水抽采（包括陆上及近海区域）未基于现有地下水水文过程线趋势达到准平衡响应。

本次瞬态模拟（transient simulation）时段为1970年至2012年，该时段涵盖了矿山开发前阶段以及一系列波动的气候条件，包括高于平均水平的干湿周期。选择1970年作为起始日期，可将历史地下水开采数据纳入模型，并为地下水模型预留足够的预热期，以弱化初始条件对目标时段（即2000年至2012年的率定/验证期）模型预测结果的影响。

内容摘自《吉普斯兰地下水模型报告》（Gippsland Groundwater Model report）2015年版。

**目的**

稳态率定模型代表1970年拉特罗布谷（Latrobe Valley）开发前的水文条件。基于稳态预测反映长期平衡条件（假设地下水输入与胁迫随时间保持恒定）的原理，稳态模拟过程中未分配任何地下水开采量。

**数据集历史**

全模型域的模拟1970年非承压测压水头面（potentiometric surface）与地下水位埋深分别如图114与图115所示（详见《吉普斯兰地下水模型报告》中的附图）。

将维多利亚州SAFE地下水位埋深图（图116）与稳态模拟地下水位埋深进行目视对比可知，地下水面在冲积系统（alluvial systems）中表现合理，但在部分高地位置，地下水位与地表特征的关联程度相较于维多利亚州含水层框架（Victorian Aquifer Framework, VAF）数据呈现的结果更强。由于此类区域均远超出关注区域范围，因此该差异不被视为重大问题。

需说明的是，VAF地下水位埋深图结合了地形分析与插值钻孔数据，并部分基于裸露基底区域内与溪流的邻近性推导得出。此外，VAF反映的是1990年的条件，而模拟的稳态地下水位埋深代表开发前条件。因此，相较于VAF空间图层中的报道结果，模拟的稳态地下水位埋深图预计会存在更大范围的浅埋地下水位。

本段内容摘自2015年版《吉普斯兰地下水模型报告》。

**数据集引用**

维多利亚州经济发展、就业、交通与资源部（2015）：地下水位埋深——模拟1970年稳态栅格（raster）数据集，生物区域评估源数据集。2018年10月5日查阅，http://data.bioregionalassessments.gov.au/dataset/4f343452-3dae-4184-b5f5-5690a17a82f6。