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

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行为设定的监管限值，旨在确保长期平均取水量维持在可持续水平，从而防范环境退化。

在新南威尔士州（New South Wales, NSW），此类限值由水资源共享计划（water sharing plans, WSPs）划定。每份WSP均明确某一河流水系的水资源在10年周期内的分配方案，同时还规定：
• 如何针对各河流水系开展LTAAEL合规性评估
• 哪些情形将触发不合规处置措施
• 可采取哪些合规处置手段。

自然资源委员会（Natural Resources Commission）会定期对所有WSP进行审查，以确保各河流水系的取水量符合设定限值；而墨累-达令流域管理局（Murray-Darling Basin Authority）则每年审查可持续分流限额（sustainable diversion limit, SDL）的合规情况。

为开展合规性评估，我们将通过配置为适配某水系WSP所定义的开发与管理规则的模型（下称LTAAEL模型）对LTAAEL进行建模。随后将该建模所得的LTAAEL，与当前条件下模拟得到的长期年均取水量（long-term average annual extractions, LTAAEs）进行对比——此类模拟取水量通常由年度许可取水量（annual permitted take, APT）模型生成。尽管LTAAEL涵盖多种取水类型，但合规性评估将基于总取水量开展。我们每年会采用当前最优的模型完成此项工作，评估结果将发布于DPE官网。

当某河流水系的LTAAEs超出LTAAEL时，该水系即被认定为不合规。若WSP中规定的不合规触发条件得以满足，则将启动不合规处置措施。

本次提供的数据集包含各河流水系多个监测断面的流量数据，此类数据由年度拓展版LTAAEL模型模拟生成。尽管该模型存在固有局限性，但仍能合理反映WSP运行与开发条件下的预期流量情况。该数据集可与其他关键情景模型的模拟流量进行对比，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。