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

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.

长期平均年取水限额（Long-term average annual extraction limit, LTAAEL）是针对河流系统年度取水行为设定的监管限额，旨在保障长期平均取水量处于可持续水平，进而有效防范环境退化。

在新南威尔士州（NSW），此类限额由水分配方案（Water Sharing Plans, WSPs）界定。每份水分配方案均明确某一河流系统的水资源在10年周期内的分配规则，同时还规定：
• 如何针对各河流系统开展长期平均年取水限额合规性评估
• 触发不合规处置的具体情形
• 可采取的合规处置措施。

自然资源委员会会定期对所有水分配方案进行审查，以确保各河流系统的取水量符合设定限额；而墨累-达令盆地管理局（Murray-Darling Basin Authority）则每年开展可持续分流限额（Sustainable Diversion Limit, SDL）合规性审查。

为开展合规性评估，我们将采用适配某河流系统水分配方案所定义的开发与管理规则的模型，对长期平均年取水限额进行建模（该模型称为长期平均年取水限额模型，LTAAEL model）。随后，我们将该模型计算得到的长期平均年取水限额，与当前条件下模拟得出的长期平均年取水量（Long-term average annual extractions, LTAAEs）进行比对——此类当前条件下的模拟取水量通常由年度许可取水量（Annual Permitted Take, APT）模型生成。尽管长期平均年取水限额涵盖多种取水类型，但合规性评估将基于总取水量开展。我们每年都会借助最优可用模型完成上述评估，并将评估结果发布于DPE官方网站。

若某河流系统的长期平均年取水量超出长期平均年取水限额，则该系统被认定为不合规。若水分配方案中约定的不合规触发条件得以满足，则将启动不合规处置流程。

本次提供的数据集包含各河流系统多个监测断面的流量数据，该数据由逐年拓展的长期平均年取水限额模型模拟生成。尽管该模型存在固有局限性，但仍可较为合理地反映水分配方案运行与开发条件下的预期流量情况。此类数据可与其他关键情景模型（如年度许可取水量模型或无开发模型（without development model, WOD model））模拟得到的流量数据进行比对。