Editing Coastal salinity intrusion extent

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{| class="wikitable" style="float:right; clear:right; margin:0 0 1em 1em; width:320px;"
|+ SIGNAL Earth Structured Data
|-
! Object type
| Damage Signal
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! SIGNAL Earth ID
| DS-00724
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! Observable type
| Coastal salinity intrusion extent
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! Unit
| area, fraction, or declared extent unit (Provisional unit carried from Step 2 DS-to-OT cleanup review; requires later OT curation if source-specific units diverge.)
|-
! Temporal structure
| —
|-
! Monitoring backbone
| —
|}
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refers to the spatial reach of saltwater encroachment into inland and coastal environments, including soils, aquifers, estuaries, and surface waters. This phenomenon occurs primarily due to the movement of saline ocean water inland, driven by processes such as flooding, storm surge, sea level rise, and groundwater extraction. The extent of salinity intrusion is an important environmental indicator as it affects freshwater availability, ecosystem health, agricultural productivity, and infrastructure stability in coastal zones.

Saltwater intrusion is a dynamic process influenced by natural and anthropogenic factors, including tidal cycles, storm events, and land use changes. Monitoring the extent of salinity intrusion provides critical information for managing coastal resources and assessing vulnerability to climate-related hazards. Understanding the spatial and temporal patterns of this phenomenon supports scientific research and informs adaptation strategies in coastal regions worldwide.

Within the broader context of ocean salinity and coastal environmental change, coastal salinity intrusion extent serves as a key observable state reflecting interactions between marine and terrestrial systems. This signal integrates hydrological, geological, and climatic influences that collectively determine the inland penetration of saline water.

== Geographic / System Context ==
Coastal salinity intrusion extent is relevant to diverse coastal systems globally, including estuaries, deltas, barrier islands, and coastal aquifers. These environments often feature complex hydrological interactions between freshwater and saltwater bodies. The geographic scope is not limited to a specific region but encompasses any coastal or near-coastal area where saltwater can move inland. Factors such as local topography, geology, tidal regimes, and human activities influence the patterns and severity of intrusion. Coastal aquifers along the Atlantic, Pacific, and Gulf coasts of the United States, as well as deltas such as the Mississippi and Mekong, are notable examples where salinity intrusion is a significant concern.

== Monitoring and Measurement ==
Monitoring coastal salinity intrusion extent involves a combination of field measurements, remote sensing, and modeling. Ground-based observations include monitoring groundwater salinity profiles, soil salinity levels, and estuarine water quality. Institutions such as the National Centers for Coastal Ocean Science (NCCOS) and the U.S. Geological Survey ([https://en.wikipedia.org/wiki/United_States_Geological_Survey USGS]) maintain monitoring networks and conduct systematic investigations of saltwater intrusion dynamics. The Ocean Observatories Initiative (OOI) provides oceanographic data that can support understanding of coastal salinity conditions. Additionally, laboratory analyses and sensor technologies measure salinity gradients and temporal changes. Data repositories such as those maintained by the Pacific Northwest National Laboratory (PNNL) facilitate access to relevant datasets. These combined approaches enable spatial mapping and temporal tracking of salinity intrusion.

Within the SIGNAL system, this phenomenon is treated as a defined environmental signal whose boundaries and measurement conventions are described below.

== Signal Definition ==
{{SignalTerm|type=DS|id=DS-00724|label=Coastal salinity intrusion extent}} is defined as the measured area or fraction of inland or coastal environments affected by the intrusion of saltwater into soils, aquifers, estuaries, or surface waters resulting from flooding, storm surge, or related processes. This signal quantifies the spatial extent of saline water presence beyond typical marine boundaries into freshwater or terrestrial systems.

== Boundary Conditions ==
Boundary inclusions encompass all inland and coastal zones where saline water from oceanic sources has intruded into soils, groundwater aquifers, estuarine waters, or surface freshwater bodies. This includes areas affected by episodic flooding, storm surge events, and chronic sea level rise impacts. Boundary exclusions involve regions where salinity changes are due solely to non-coastal sources such as inland mineral deposits or anthropogenic salinization unrelated to oceanic saltwater intrusion. Areas outside the influence of tidal or marine salinity are also excluded.

== Aggregation Semantics ==
Geographic aggregation of coastal salinity intrusion extent involves spatially integrating measurements across coastal zones, aquifers, and estuarine systems to produce regional or national scale assessments. Temporal aggregation may consider daily, seasonal, or event-based intervals depending on monitoring frequency and the dynamics of intrusion processes. Cross-signal aggregation relates this signal to others such as coastal flood inundation extent and sea surface salinity to understand compound effects and drivers. Aggregated data support multi-scale analysis of coastal salinity impacts and trends.

== Observational Status ==
Current monitoring efforts provide intermittent to continuous data on coastal salinity intrusion in selected regions, supported by institutional programs and research initiatives. However, comprehensive global monitoring networks remain limited, and temporal resolution varies by location and method. Future SIGNAL releases may incorporate improved temporal structures, expanded geographic coverage, and integration with related environmental signals to enhance the characterization of salinity intrusion dynamics and impacts.

== Related Signals ==
* Coastal flood inundation extent
* Coastal storm surge height
* Drinking-water service disruption duration
* Global mean sea level
* Household water insecurity prevalence
* Saline and brine discharge to receiving waters
* Sea surface salinity
* Surface freshwater availability

== Key People ==
* National Centers for Coastal Ocean Science (NCCOS)
* U.S. Geological Survey (USGS)
* Ocean Observatories Initiative (OOI)
* Pacific Northwest National Laboratory (PNNL)

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== Key Associated People ==
* '''Matthew D. Petkewich''' — U.S. Geological Survey [Supporting contributor; High]
* '''Paul M. Barlow''' — U.S. Geological Survey [Supporting contributor; High]

Inclusion reflects material contribution to the scientific understanding of this damage signal; it does not imply review, endorsement, or affiliation with SIGNAL Earth.
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== Sources ==
* [https://www.usgs.gov/data/coastal-salinity-index-monitoring-drought Coastal Salinity Index for Monitoring Drought] — U.S. Geological Survey Data Release, 2019. DOI: 10.5066/P9MQLNL2. [Dataset; Supporting; High]
* [https://www.nature.com/articles/s41467-020-17038-2 Groundwater level observations in 250,000 coastal US wells reveal scope of potential seawater intrusion] — Nature Communications, 2020. DOI: 10.1038/s41467-020-17038-2. [Paper; Supporting; High]
* [https://www.usgs.gov/publications/saltwater-intrusion-coastal-regions-north-america Saltwater intrusion in coastal regions of North America] — Hydrogeology Journal, 2010. DOI: 10.1007/s10040-009-0514-3. [Paper; Supporting; High]
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