Landscape controls on surface water quality

sourcepathwaydestination Stream ecology Landscape ecology precip

Variation in source water -Related to land use -Ionic composition (N, S) and pH

Landscape control on surface water quality is all about… Pathway of water from land to water body –As water moves from one place to another: Physical changes –Particulate accumulation/removal –Leaching Chemical transformations (biogeochemistry) –Different patches cause different types, amounts of physical, chemical change

source pathway destination Patch composition Patch size Patch arrangement

Effects of pathway (landscape structure) on water quality How pathway composition varies across large areas

Effects of landscape elements (patches) on water chemistry 1. Parent geology Variation in parent geology, weathering ---> chemical variation in water Sandstone + dolomite dolomite Mixed granites Dolomite, shale, limestone

From: Jones, J.B Freshwater Biology 47:

Geology/weathering effects Cations –In particular: Ca, Mg, Si Anions –Carbonates productivity, acidification risk Nutrients –Phosphorus all from rock weathering Slow rate of weathering  widespread P limitation –Nitrogen Geological effects exist within, between drainages

From: Holloway et al Nature 395:

Geology/weathering effects Effects of parent geology on the path that water takes –Preferential flow paths –Land forms

Effects of landscape elements (patches) on water chemistry 2. Land Use/Land Cover Variation in land use/land cover ---> variation in water quality *Best studied landscape effect on water quality

Land use-water quality relationships % Agriculture in the basin (Stanley unpublished)

Signal of agricultural, urban land cover is often strong and direct –Nutrient enrichment –Classic pollutants –Organic C % agriculture But not always…

When water quality is not predictable from land cover H 1 : Hydrologic pathways by-pass land cover

What we see… What actually happens (Deep) groundwater sources by-passing land cover

Hydrology + landscape ecology There are many ways for water to flow downhill

When water quality is not predictable from land cover H 2 : Flowpaths vary as a function of landscape position –Water quality varies among lakes despite similar land cover Different lakes fed by water from different sources

Landscape position related to lake hydrology Precipitation Input Groundwater Input “Highland” lake “Lowland” lake

High (little GW) Low (lots of GW) Cond (µS cm -1 ) Landscape position Chl a (µ g L -1 ) Landscape position High (little GW) Low (lots of GW) From: Riera et al Freshwater Biology 43:

When water quality is not predictable from land cover H 3 : Hot spot effects –Patches that have a disproportionately large influence on water quality Addition of particles, solutes Removal of particles, solutes

Hot spots 1. Sites where water moves quickly from land to lake/stream

P derived from small hotspots (“effective areas”) Extent of hotspots affected by land use –Urban cover accounts for: 10% of cover 20-55% of P input to L. Mendota From:Soranno et al Ecological Applications 6:

Hot spots 2. Sites where water is subject to distinct physical/biogeochemical environment, intensive change  ecotones

Riparian zones Aquatic/terrestrial interface –Soils often saturated (anoxic), rich in OM –Water velocity slows Rapid bgc change, particle trapping NO 3 -N (ug/L) UP RM RO

Riparian zones Solution to non-point source pollution? –Sometimes… May or may not be effective in reducing nutrient loads in groundwater –Pathways –Size, shape of RZ

The challenge- determining when water does/does not pass through the riparian zone

Spatial configuration of riparian zone affects nutrient retention From: Weller et al Ecological Applications 8:

Landscape influence on water quality determined by: -Relative importance of different flowpaths -What happens along these flow path - Lots of research opportunities for questions re: -patch arrangement, patch size precip deep gw