Rtuffli: SIGNAL publish from draft v728

2026-06-08T23:22:30Z

SIGNAL publish from draft v728

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{| class="wikitable" style="float:right; clear:right; margin:0 0 1em 1em; width:320px;"
|+ SIGNAL Earth Structured Data
|-
! Object type
| Causal Mechanism
|-
! SIGNAL Earth ID
| CMECH-0005
|-
! Mechanism family
| hydrologic transport
|-
! Role
| Reusable causal pathway
|-
! Mapped causal edges
| 72
|-
! Article priority
| Shared Mechanism Article
|-
! Article status
| Published
|-
! Review status
| Proposed
|}


is a causal mechanism describing how the movement and routing of water through freshwater, coastal, and terrestrial systems convey environmental pressures, such as pollutants, nutrients, sediments, and contaminants, from their sources to downstream locations. This mechanism explains how upstream activities and natural processes influence downstream environmental conditions by transporting materials via runoff, infiltration, discharge, storage, and flow pathways. It is distinct from accounting or proxy relationships by focusing on the physical movement of water as the vector for propagating pressures across connected ecosystems and human systems.

== Signal Relationships ==
Upstream Damage Signals related to water quantity and quality, such as river discharge, groundwater storage, and extreme precipitation, physically cause or contribute to downstream Damage Signals including surface freshwater availability, flood extent, contaminant loads, and disease incidence rates. For example, increased river discharge at a basin outlet causes expanded flooded area extent and increased surface freshwater availability downstream. Similarly, extreme precipitation intensity causes urban flood inundation extent and increases urban stormwater contaminant and pathogen loads by mobilizing pollutants. These relationships reflect direct physical causality through hydrologic pathways rather than accounting or diagnostic correlations.

== Mechanism Pathway ==
The mechanism operates through the hydrologic cycle and landscape connectivity. Water collects precipitation and surface runoff, infiltrates soils, recharges groundwater, and flows through rivers and streams, transporting dissolved and particulate environmental pressures. These pressures include nutrients from agricultural runoff, metals from mining drainage, pathogens from urban stormwater, and sediments from erosion. Hydrologic transport routes pressures from their sources to downstream receptors, where they accumulate, dilute, or transform. Storage components like snowpack and groundwater modulate timing and magnitude of transport by delaying or sustaining flows. Urban impervious surfaces and flood inundation alter flow paths and velocities, amplifying contaminant mobilization. This pathway physically links upstream environmental pressures to downstream impacts via water movement.

== Scientific Basis ==
The scientific basis derives from hydrology, watershed science, and environmental chemistry. Empirical observations and modeling studies demonstrate how precipitation intensity, river discharge, groundwater levels, and soil moisture govern water flow volumes and velocities, which in turn control transport and fate of pollutants and sediments. Numerous peer-reviewed studies document the linkage between hydrologic variables and downstream water quality, ecosystem productivity, and human health outcomes. For example, studies show that extreme precipitation events overwhelm urban drainage systems causing combined sewer overflows, and that snowmelt runoff contributes to seasonal river discharge sustaining freshwater availability. These findings are supported by remote sensing, in situ monitoring, and hydrologic modeling.

== Scope and Boundary Conditions ==
This mechanism applies primarily within freshwater and coastal hydrologic systems where surface and subsurface water flows connect source areas to downstream environments. It encompasses natural and anthropogenic pressures transported by water movement, including nutrients, metals, pathogens, sediments, and plastics. The mechanism’s relevance depends on hydrologic connectivity, landscape characteristics, and human infrastructure. It may be limited or modified by factors such as water management interventions, engineered barriers, or non-hydrologic transport pathways (e.g., atmospheric deposition). The spatial scale ranges from local watersheds to large river basins and coastal zones. Temporal scales vary from event-based transport during storms to seasonal snowmelt and long-term groundwater flow.

== Lag and Persistence ==
Transport lags vary by pathway and storage components. Surface runoff and river discharge can convey pressures within hours to days following precipitation events, resulting in short lag times for flood-related impacts. Groundwater transport involves longer lags from months to years due to slower flow velocities and storage in aquifers. Snowpack and glacier melt introduce seasonal lags by storing water and releasing it during melt periods. Persistence of transported pressures downstream depends on dilution, degradation, sedimentation, and biogeochemical transformations. Some contaminants may accumulate and persist in sediments or biota, extending environmental effects beyond transport durations.

== Thresholds and Nonlinearities ==
Nonlinearities arise from threshold behaviors in hydrologic transport. For example, extreme precipitation intensity exceeding drainage capacity triggers combined sewer overflows and urban flooding, causing abrupt increases in contaminant loads. Similarly, soil saturation thresholds influence runoff generation, with dry soils absorbing rainfall until saturation is reached, after which runoff sharply increases. Urban impervious surfaces reduce infiltration thresholds, increasing runoff volumes nonlinearly. Floodplain activation occurs when river discharge exceeds channel capacity, causing rapid expansion of flooded areas. These threshold effects produce nonlinear responses in downstream Damage Signals relative to upstream hydrologic drivers.

== Uncertainty and Contestability ==
Uncertainties stem from spatial heterogeneity in hydrologic pathways, temporal variability in precipitation and flow regimes, and incomplete knowledge of contaminant sources and transformations. Measurement limitations and model assumptions contribute to uncertainty in quantifying transport magnitudes and timing. The relative importance of different transport routes (surface vs. subsurface) may vary by context. Contestability arises in attributing downstream impacts solely to hydrologic transport when other mechanisms such as atmospheric deposition or direct point-source discharges also contribute. Additionally, human interventions like dams, diversions, and wastewater treatment modify transport pathways and effects, complicating causal attribution.

== Related Signal Edges ==
* [[Coal extraction rate|DS-00033 Coal extraction rate]] --contributes_to--> [[Mine drainage and metal-bearing water discharge|DS-00803 Mine drainage and metal-bearing water discharge]]
* [[Crop-days under drought stress|DS-00092 Crop-days under drought stress]] --contributes_to--> DS-00743 Crop yield gap index
* DS-00712 Drought severity index --amplifies--> [[Intensity ratio of cropland irrigation withdrawal to renewable water supply|DS-00383 Intensity ratio of cropland irrigation withdrawal to renewable water supply]]
* DS-00712 Drought severity index --dampens--> [[Net primary productivity (NPP)|DS-00116 Net primary productivity (NPP)]]
* DS-00720 Extreme precipitation intensity --causes--> DS-00761 Combined sewer overflow discharge volume
* DS-00720 Extreme precipitation intensity --contributes_to--> DS-00767 Urban stormwater contaminant load
* DS-00720 Extreme precipitation intensity --contributes_to--> DS-00770 Urban stormwater pathogen load
* DS-00720 Extreme precipitation intensity --contributes_to--> DS-00728 Vector-borne disease incidence rate
* DS-00720 Extreme precipitation intensity --contributes_to--> DS-00729 Waterborne disease incidence rate
* [[Flooded area extent|DS-00142 Flooded area extent]] --contributes_to--> DS-00728 Vector-borne disease incidence rate
* [[Flooded area extent|DS-00142 Flooded area extent]] --contributes_to--> DS-00729 Waterborne disease incidence rate
* [[Global mean sea level|DS-00003 Global mean sea level]] --contributes_to--> [[Flooded area extent|DS-00142 Flooded area extent]]
* [[Intensity ratio of cropland irrigation withdrawal to renewable water supply|DS-00383 Intensity ratio of cropland irrigation withdrawal to renewable water supply]] --amplifies--> [[Crop-days under drought stress|DS-00092 Crop-days under drought stress]]
* [[Marine plastic concentration|DS-00736 Marine plastic concentration]] --contributes_to--> DS-00737 Coastal litter accumulation density
* [[Plastic waste leakage to marine environment|DS-00079 Plastic waste leakage to marine environment]] --contributes_to--> [[Marine plastic concentration|DS-00736 Marine plastic concentration]]
* [[Primary copper ore extraction rate|DS-00035 Primary copper ore extraction rate]] --contributes_to--> [[Mine drainage and metal-bearing water discharge|DS-00803 Mine drainage and metal-bearing water discharge]]
* [[River discharge at basin outlet|DS-00015 River discharge at basin outlet]] --causes--> DS-00710 Surface freshwater availability
* [[Soil moisture content|DS-00148 Soil moisture content]] --contributes_to--> [[Net primary productivity (NPP)|DS-00116 Net primary productivity (NPP)]]
* DS-00710 Surface freshwater availability --dampens--> [[Intensity ratio of cropland irrigation withdrawal to renewable water supply|DS-00383 Intensity ratio of cropland irrigation withdrawal to renewable water supply]]
* [[Tailings Mass Generated Rate|DS-00036 Tailings mass generated rate]] --contributes_to--> [[Mine drainage and metal-bearing water discharge|DS-00803 Mine drainage and metal-bearing water discharge]]
* DS-00731 Urban flood inundation extent --contributes_to--> DS-00768 Road runoff contaminant load
* DS-00731 Urban flood inundation extent --amplifies--> DS-00767 Urban stormwater contaminant load
* DS-00731 Urban flood inundation extent --amplifies--> DS-00770 Urban stormwater pathogen load
* DS-00720 Extreme precipitation intensity --contributes_to--> [[Sediment flux to rivers/coasts|DS-00145 Sediment flux to rivers/coasts]]
* [[Groundwater Storage Volume|DS-00132 Groundwater storage volume]] --contributes_to--> DS-00710 Surface freshwater availability
* DS-00715 Snowpack water equivalent --contributes_to--> [[River discharge at basin outlet|DS-00015 River discharge at basin outlet]]
* [[Soil moisture content|DS-00148 Soil moisture content]] --dampens--> DS-00726 Desertification severity index
* [[Groundwater level (water table depth)|DS-00014 Groundwater level (water table depth)]] --contributes_to--> DS-00710 Surface freshwater availability
* DS-00715 Snowpack water equivalent --contributes_to--> DS-00710 Surface freshwater availability
* [[Freshwater Withdrawal Volume Flux|DS-00050 Freshwater withdrawal volume flux]] --dampens--> DS-00710 Surface freshwater availability
* DS-00715 Snowpack water equivalent --dampens--> DS-00712 Drought severity index
* DS-00720 Extreme precipitation intensity --causes--> DS-00775 Pesticide runoff concentration
* [[Freshwater Withdrawal Volume Flux|DS-00050 Freshwater withdrawal volume flux]] --causes--> DS-00711 Water withdrawal-to-availability ratio
* DS-00710 Surface freshwater availability --dampens--> DS-00711 Water withdrawal-to-availability ratio
* [[Glacier Area Extent|DS-00121 Glacier area extent]] --contributes_to--> DS-00716 Snowmelt runoff contribution
* [[Ice volume (glaciers)|DS-00125 Ice volume (glaciers)]] --contributes_to--> DS-00716 Snowmelt runoff contribution
* [[Groundwater Extraction Rate|DS-00082 Groundwater extraction rate]] --dampens--> [[Groundwater Storage Volume|DS-00132 Groundwater storage volume]]
* DS-00716 Snowmelt runoff contribution --contributes_to--> [[River discharge at basin outlet|DS-00015 River discharge at basin outlet]]
* [[Groundwater Extraction Rate|DS-00082 Groundwater extraction rate]] --dampens--> [[Groundwater level (water table depth)|DS-00014 Groundwater level (water table depth)]]
* DS-00756 Municipal solid waste leakage rate --contributes_to--> DS-00737 Coastal litter accumulation density
* DS-00756 Municipal solid waste leakage rate --contributes_to--> [[Marine plastic concentration|DS-00736 Marine plastic concentration]]
* DS-00716 Snowmelt runoff contribution --contributes_to--> DS-00710 Surface freshwater availability
* DS-00731 Urban flood inundation extent --amplifies--> DS-00757 Landfill leachate contamination load
* DS-00731 Urban flood inundation extent --amplifies--> DS-00756 Municipal solid waste leakage rate
* DS-00731 Urban flood inundation extent --contributes_to--> DS-00758 Urban litter accumulation density
* [[Glacier Area Extent|DS-00121 Glacier area extent]] --contributes_to--> DS-00710 Surface freshwater availability
* [[Soil moisture content|DS-00148 Soil moisture content]] --dampens--> DS-00712 Drought severity index
* [[Ice volume (glaciers)|DS-00125 Ice volume (glaciers)]] --contributes_to--> DS-00710 Surface freshwater availability
* [[Riverine nitrate concentration (NO3-)|DS-00134 Riverine nitrate concentration (NO3-)]] --contributes_to--> DS-00707 Coastal eutrophication index
* [[Riverine Total Phosphorus Concentration (TP)|DS-00135 Riverine total phosphorus concentration (TP)]] --contributes_to--> DS-00707 Coastal eutrophication index
* [[Synthetic nitrogen fertilizer application rate|DS-00039 Synthetic nitrogen fertilizer application rate]] --contributes_to--> DS-00709 Groundwater nitrate concentration
* DS-00709 Groundwater nitrate concentration --contributes_to--> [[Drinking-water nitrate concentration (point of use)|DS-00091 Drinking-water nitrate concentration (point of use)]]
* [[Urban impervious surface area|DS-00072 Urban impervious surface area]] --contributes_to--> DS-00731 Urban flood inundation extent
* DS-00720 Extreme precipitation intensity --causes--> DS-00731 Urban flood inundation extent
* [[Flooded area extent|DS-00142 Flooded area extent]] --contributes_to--> DS-00731 Urban flood inundation extent
* [[Agricultural nitrate runoff load to receiving waters|DS-00816 Agricultural nitrate runoff load to receiving waters]] --causes--> [[Nitrogen runoff flux to water|DS-00083 Nitrogen runoff flux to water]]
* [[Agricultural phosphorus runoff load to receiving waters|DS-00817 Agricultural phosphorus runoff load to receiving waters]] --causes--> [[Phosphorus Load Flux to Water|DS-00084 Phosphorus load flux to water]]
* [[Contaminated operational runoff to receiving waters|DS-00805 Contaminated operational runoff to receiving waters]] --contributes_to--> DS-00776 Freshwater ecotoxicity burden index
* [[Crude oil extraction rate|DS-00031 Crude oil extraction rate]] --contributes_to--> [[Contaminated operational runoff to receiving waters|DS-00805 Contaminated operational runoff to receiving waters]]
* [[Crude oil extraction rate|DS-00031 Crude oil extraction rate]] --contributes_to--> [[Industrial contaminated wastewater discharge to receiving waters|DS-00802 Industrial contaminated wastewater discharge to receiving waters]]
* [[Crude oil extraction rate|DS-00031 Crude oil extraction rate]] --contributes_to--> [[Saline and brine discharge to receiving waters|DS-00806 Saline and brine discharge to receiving waters]]
* DS-00720 Extreme precipitation intensity --causes--> [[Cumulative Exceedance Duration of Extreme Rainfall Intensity (Above Declared Percentile Threshold)|DS-00376 Cumulative exceedance duration of extreme rainfall intensity (above declared percentile threshold)]]
* DS-00720 Extreme precipitation intensity --contributes_to--> [[Flooded area extent|DS-00142 Flooded area extent]]
* DS-00720 Extreme precipitation intensity --contributes_to--> [[River discharge at basin outlet|DS-00015 River discharge at basin outlet]]
* [[Intensity ratio of cropland irrigation withdrawal to renewable water supply|DS-00383 Intensity ratio of cropland irrigation withdrawal to renewable water supply]] --causes--> DS-00778 Irrigation return-flow nutrient load
* DS-00778 Irrigation return-flow nutrient load --contributes_to--> [[Drinking-water nitrate concentration (point of use)|DS-00091 Drinking-water nitrate concentration (point of use)]]
* DS-00778 Irrigation return-flow nutrient load --contributes_to--> DS-00709 Groundwater nitrate concentration
* DS-00778 Irrigation return-flow nutrient load --contributes_to--> [[Riverine nitrate concentration (NO3-)|DS-00134 Riverine nitrate concentration (NO3-)]]
* [[Natural gas extraction rate|DS-00032 Natural gas extraction rate]] --contributes_to--> [[Contaminated operational runoff to receiving waters|DS-00805 Contaminated operational runoff to receiving waters]]
* [[Natural gas extraction rate|DS-00032 Natural gas extraction rate]] --contributes_to--> [[Industrial contaminated wastewater discharge to receiving waters|DS-00802 Industrial contaminated wastewater discharge to receiving waters]]
* [[Natural gas extraction rate|DS-00032 Natural gas extraction rate]] --contributes_to--> [[Saline and brine discharge to receiving waters|DS-00806 Saline and brine discharge to receiving waters]]
* [[River discharge at basin outlet|DS-00015 River discharge at basin outlet]] --contributes_to--> [[Flooded area extent|DS-00142 Flooded area extent]]

== Related Signal Nodes ==
* [[Coal extraction rate|DS-00033 Coal extraction rate]]
* [[Mine drainage and metal-bearing water discharge|DS-00803 Mine drainage and metal-bearing water discharge]]
* [[Crop-days under drought stress|DS-00092 Crop-days under drought stress]]
* DS-00743 Crop yield gap index
* DS-00712 Drought severity index
* [[Intensity ratio of cropland irrigation withdrawal to renewable water supply|DS-00383 Intensity ratio of cropland irrigation withdrawal to renewable water supply]]
* [[Net primary productivity (NPP)|DS-00116 Net primary productivity (NPP)]]
* DS-00720 Extreme precipitation intensity
* DS-00761 Combined sewer overflow discharge volume
* DS-00767 Urban stormwater contaminant load
* DS-00770 Urban stormwater pathogen load
* DS-00728 Vector-borne disease incidence rate
* DS-00729 Waterborne disease incidence rate
* [[Flooded area extent|DS-00142 Flooded area extent]]
* [[Global mean sea level|DS-00003 Global mean sea level]]
* [[Marine plastic concentration|DS-00736 Marine plastic concentration]]
* DS-00737 Coastal litter accumulation density
* [[Plastic waste leakage to marine environment|DS-00079 Plastic waste leakage to marine environment]]
* [[Primary copper ore extraction rate|DS-00035 Primary copper ore extraction rate]]
* [[River discharge at basin outlet|DS-00015 River discharge at basin outlet]]
* DS-00710 Surface freshwater availability
* [[Soil moisture content|DS-00148 Soil moisture content]]
* [[Tailings Mass Generated Rate|DS-00036 Tailings mass generated rate]]
* DS-00731 Urban flood inundation extent
* DS-00768 Road runoff contaminant load
* [[Sediment flux to rivers/coasts|DS-00145 Sediment flux to rivers/coasts]]
* [[Groundwater Storage Volume|DS-00132 Groundwater storage volume]]
* DS-00715 Snowpack water equivalent
* DS-00726 Desertification severity index
* [[Groundwater level (water table depth)|DS-00014 Groundwater level (water table depth)]]
* [[Freshwater Withdrawal Volume Flux|DS-00050 Freshwater withdrawal volume flux]]
* DS-00775 Pesticide runoff concentration
* DS-00711 Water withdrawal-to-availability ratio
* [[Glacier Area Extent|DS-00121 Glacier area extent]]
* DS-00716 Snowmelt runoff contribution
* [[Ice volume (glaciers)|DS-00125 Ice volume (glaciers)]]
* [[Groundwater Extraction Rate|DS-00082 Groundwater extraction rate]]
* DS-00756 Municipal solid waste leakage rate
* DS-00757 Landfill leachate contamination load
* DS-00758 Urban litter accumulation density
* [[Riverine nitrate concentration (NO3-)|DS-00134 Riverine nitrate concentration (NO3-)]]
* DS-00707 Coastal eutrophication index
* [[Riverine Total Phosphorus Concentration (TP)|DS-00135 Riverine total phosphorus concentration (TP)]]
* [[Synthetic nitrogen fertilizer application rate|DS-00039 Synthetic nitrogen fertilizer application rate]]
* DS-00709 Groundwater nitrate concentration
* [[Drinking-water nitrate concentration (point of use)|DS-00091 Drinking-water nitrate concentration (point of use)]]
* [[Urban impervious surface area|DS-00072 Urban impervious surface area]]
* [[Agricultural nitrate runoff load to receiving waters|DS-00816 Agricultural nitrate runoff load to receiving waters]]
* [[Nitrogen runoff flux to water|DS-00083 Nitrogen runoff flux to water]]
* [[Agricultural phosphorus runoff load to receiving waters|DS-00817 Agricultural phosphorus runoff load to receiving waters]]
* [[Phosphorus Load Flux to Water|DS-00084 Phosphorus load flux to water]]
* [[Contaminated operational runoff to receiving waters|DS-00805 Contaminated operational runoff to receiving waters]]
* DS-00776 Freshwater ecotoxicity burden index
* [[Crude oil extraction rate|DS-00031 Crude oil extraction rate]]
* [[Industrial contaminated wastewater discharge to receiving waters|DS-00802 Industrial contaminated wastewater discharge to receiving waters]]
* [[Saline and brine discharge to receiving waters|DS-00806 Saline and brine discharge to receiving waters]]
* [[Cumulative Exceedance Duration of Extreme Rainfall Intensity (Above Declared Percentile Threshold)|DS-00376 Cumulative exceedance duration of extreme rainfall intensity (above declared percentile threshold)]]
* DS-00778 Irrigation return-flow nutrient load
* [[Natural gas extraction rate|DS-00032 Natural gas extraction rate]]

== Key Researchers / Contributors to the Literature ==
* Provisional; requires steward review

== Sources and Key Academic Articles ==
* [https://essd.copernicus.org/articles/17/4305/2025/ ESA CCI Soil Moisture GAPFILLED: an independent global gap-free satellite climate data record with uncertainty estimates (2025]
* [https://www.nature.com/articles/s41586-024-07758-6 A local-to-global emissions inventory of macroplastic pollution (2024]
* [https://doi.org/10.3390/rs16244692 Detection of the Contribution of Vegetation Change to Global Net Primary Productivity: A Satellite Perspective (2024) https://doi.org/10.3390/rs16244692]
* [https://www.mdpi.com/2071-1050/14/24/16896 Global Assessment of Groundwater Stress Vis-à-Vis Irrigated Food Production (2022]
* [https://doi.org/10.1111/plb.13304 Drought and crop yield (2021) https://onlinelibrary.wiley.com/doi/full/10.1111/plb.13304]
* [https://doi.org/10.1126/science.aba3996 Globally observed trends in mean and extreme river flow (2021) https://www.science.org/doi/10.1126/science.aba3996]
* [https://openknowledge.worldbank.org/ What a Waste 2.0: A Global Snapshot of Solid Waste Management to 2050 (2018]
* [https://doi.org/10.1126/science.1185782 The rate of sea-level rise (2010) https://doi.org/10.1126/science.1185782]
* [https://doi.org/10.1038/35066500 Sea-level rise and variability from satellite altimetry (2001) https://doi.org/10.1038/35066500]
* [https://www.energyinst.org/ BP Statistical Review / Energy Institute review (coal]
* [https://globaltailingsreview.org/ Global Tailings Review (ICMM/UNEP/PRI]
* [https://www.icsg.org/ International Copper Study Group (ICSG) statistics]
* [https://doi.org/10.1016/j.resconrec.2009.12.007 Mudd 2010 copper mining sustainability review https://doi.org/10.1016/j.resconrec.2009.12.007]
* [https://doi.org/10.1016/j.jhazmat.2007.09.012 Rico et al. 2008 tailings dam failures dataset https://doi.org/10.1016/j.jhazmat.2007.09.012]
* [https://www.eia.gov/coal/ US EIA coal production data]
* [https://www.usgs.gov/centers/national-minerals-information-center USGS mineral commodity summaries: Copper]
* [https://www.unep.org/ World Bank / UNEP hazardous waste reports]
* [https://www.mdpi.com/2071-1050/14/24/16896 Global Assessment of Groundwater Stress Vis-à-Vis Irrigated Food Production (2022]

== Wikipedia Context ==
Wikipedia provides general background on hydrologic transport, hydrology, and environmental pollution concepts, describing the processes of water movement and its role in transporting substances through ecosystems. This SIGNAL article specifically explains how hydrologic transport functions as a causal mechanism linking upstream environmental pressures to downstream Damage Signals within the SIGNAL causal graph framework, emphasizing physical causality rather than proxy or accounting relationships.

* https://en.wikipedia.org/wiki/Hydrology
* https://en.wikipedia.org/wiki/Water_cycle
* https://en.wikipedia.org/wiki/Runoff
* https://en.wikipedia.org/wiki/Water_pollution
* https://en.wikipedia.org/wiki/Environmental_pollution

Hydrologic transport of environmental pressures - Revision history

Rtuffli: SIGNAL publish from draft v728