Water Modelling-Modelled Data-Long-term average annual extraction limit (LTAAEL)

Long-term average annual extraction limit (LTAAEL) is a regulatory limit set on annual water extractions from a river system. It ensures that average extractions over the long term are sustainable, and thus help prevent environmental degradation.\r\n\r\nIn NSW these limits are defined by water sharing plans (WSPs). Every WSP outlines how the water in a river system will be shared over a 10-year period. They also define:\r\n\r\n• how LTAAEL compliance is to be assessed for each river system\r\n\r\n• what conditions will trigger noncompliance action\r\n\r\n• what compliance action can be taken.\r\n\r\nThe Natural Resources Commission regularly reviews all WSPs to ensure extractions from each river system are within the limits set, and the Murray-Darling Basin Authority reviews sustainable diversion limit (SDL) compliance each year.\r\n\r\nTo assess compliance, we model LTAAEL using a model that has been configured to represent the development and management rules defined by a system WSP (this refers to as LTAAEL model). We then compare this modelled LTAAEL with the modelled under current conditions long-term average annual extractions (LTAAEs) (which are usually those modelled by the annual permitted take, or APT, model). Although, the LTAAEL includes multiple types of water use, the compliance assessment is based on the total. We do this annually using the best available models, and the outcomes are published on the DPE website.\r\n\r\nWhere river system’s LTAAE exceed LTAAEL, the system is considered noncompliant. If the noncompliance trigger conditions in the WSP are met, noncompliance action is taken.\r\n\r\nThe data set provided contains flows at several gauges in each river system, as simulated by the annually extended LTAAEL model. Notwithstanding the model’s inherent limitations, these are a fair representation of those we would expect under WSP operation and development conditions. They can be compared with flows simulated by other key scenario models, such as annual permitted take (APT) model or without development (WOD) model.

长期年均取水限额（Long-term Average Annual Extraction Limit, LTAAEL）是为河流水系年度取水设置的监管限值，旨在保障长期平均取水行为具备可持续性，进而助力防范环境退化。

新南威尔士州（New South Wales, NSW）的此类限值由《水资源共享计划》（Water Sharing Plans, WSPs）制定。每项《水资源共享计划》均明确了河流水系水资源在10年周期内的分配方案，同时还规定了以下内容：
• 各河流水系长期年均取水限额合规性的评估方式
• 触发违规处置的情形
• 可采取的合规处置措施

自然资源委员会（Natural Resources Commission）会定期对所有《水资源共享计划》开展审查，以确保各河流水系的取水行为符合既定限值；墨累-达令流域管理局（Murray-Darling Basin Authority）则每年都会对可持续分流限额（Sustainable Diversion Limit, SDL）的合规情况进行核查。

合规性评估环节中，研究团队会采用适配河流水系《水资源共享计划》所规定的开发与管理规则的模型，对长期年均取水限额进行模拟，该模型即称为LTAAEL模型。随后将模拟得到的长期年均取水限额，与当前情境下模拟得到的长期年均取水量（Long-term Average Annual Extractions, LTAAEs）进行对比——此类取水量通常由年度许可取水量（Annual Permitted Take, APT）模型模拟得出。尽管长期年均取水限额涵盖多种取水类型，但合规性评估将以总取水量为依据。该项评估每年都会采用当前最优的模型开展，评估结果将发布于规划与环境部（Department of Planning and Environment, DPE）官方网站。

当某河流水系的长期年均取水量超出长期年均取水限额时，该水系即被认定为不合规。若满足《水资源共享计划》中规定的违规触发条件，则将启动违规处置流程。

本次提供的数据集包含各河流水系多个水文监测站的流量数据，此类数据由年度迭代的LTAAEL模型模拟生成。尽管该模型存在固有局限性，但上述流量数据仍能合理反映《水资源共享计划》运行与开发情境下的预期流量水平，可将此类数据与其他关键情境模型模拟得到的流量进行对比，例如年度许可取水量（APT）模型或无开发（Without Development, WOD）模型的模拟结果。