Groundwater and Geology of Southwest Wisconsin

Paul Ohlrogge UW-Extension Iowa County

This presentation describes southwest Wisconsin’s geology and its groundwater resources.

Geology

Groundwater quantity and quality

2

ROAD CUT IN SINNIPEE GROUP, HWY 151 IOWA CO.

Groundwater in southwest Wisconsin… …provides drinking water.

… sustains the environment, the economy, and our quality of life. HydrologicWater cycle Cycle

Recharge

Aquifer The hydrologic cycle in the Driftless Area is more complex due to extensive aquitards.

Perched aquifer aquitard

Deep aquifer Groundwater discharge sustains baseflow to streams and springs year-round.

Stephens Falls, Governor Dodge

Big Spring, Iowa County The Decorah-Platteville aquitard separates the shallow Galena aquifer from the deep aquifer.

Springs may develop along valley walls at times of high water table. There are three major aquifers in Iowa County.

sand and gravel

deep aquifer

Galena aquifer In upland areas, well construction MUST exceed state requirements for casing depth. Shallow cased wells are legal but make people sick.

Well 1 Well 2 Well 3 Groundwater flows from high to low elevations.

One use of the water table map is to identify where groundwater comes from that flows to a well or stream. Groundwater recharge rates are high in Iowa County, due to permeable soil, and forest and agricultural land use.

Infiltration, in an average year

Infiltration, medium (6 - 9in inches/year) an average year

high (9 - 11 inches/year)medium (6 - 9 inches/year) high (9 - 11 inches/year)

very high (> 11 inches/year)very high (> 11 inches/year)

not defined (wetland or water) 0 1 2 3 Miles 0 1 2 3 Miles Does this mean that there is an unlimited supply of water? Ü

21 Ü Groundwater in dolomite and limestone is vulnerable to contamination.

Caves, sinkholes and fractures are pathways for contaminants to quickly reach the water table. Deeply-cased wells provide some protection from such fractures. !# !# k !# k ! ! ! k # k ! ! !#!!# k k !# ! k k # k ! ! k ! k k # ! k ! ! # !#!!# k k ! k ! # # # # k # k # k# k ! !!# k# k k# k # k k#k ! k# !k kk !# k k kk k kk## ! #! # # # k k k# k # k k k # k# k ! !!!# k k# k k# k k # k#k k# !k kk kk !# # k k k ! k kk# k k k k kk##k ! # k k# k k k k k! k ! k k#k k k k k k k k kk # # k k ! k # # k k k k k k k k Groundwater # k # k k k! #k k k#k k kk ! ! k kk k k k # # k k k # kk k # k k # !# k# k # k# k k k # ! # k k k k k k #k #k ! k k k k k # k susceptibility to !# k k # k # k # # k k# k k # k# k k kk k # ! ! ! k # k k k k k # k ! !k# !k#!!# # k k ! kk k k k k k # k # k # # #k k k#k # # # k # k k k k k k # # k k contamination k k ## ! k## k# # k # k k k # ! # # k # k # # #k k k kk # k # # k# k ! !!# k# k # k# k k # k kk#k # # kk k# !k kk # # !# k k # k # k kk k k ## # # k # #kk## ! k# k k # k k# k k # k k ! k # k k k # kk kkk kk # # ! k k k Susceptibility # ! # k # #k k k ! ### #k #k # # # k kk k # k k k k k k k k k# k ## k k# # k kkk# # k # k k k k k# k! ! k k k k k k k #k k kk Least susceptible k k k k # # k k #k # # # #k k k # ! k k # # # k ##k k k # # k k k k k # # #k # #! k kk k# # #k k## k #k # k k# Moderately susceptible # ! !k # k !k# #k#kk k #k # #k k k # k #k # # k k # # #! # k# kk k# k ## # # k k # # # k k #k # k k # k k k k k # # #k Highly susceptible # k k k !# kk k k # k #k k# ## # # k k # # k # # k k #k k k # k# k# k## # # k # k k k # # # k k k k k # k #k # k# k Most susceptible ## # kk k k#k kk#k # # k # # k # # # #k k # kk# k# k # k k k# k # k # k k # #k # k # ! k #k # k# # # k k k k k ## !k k !k k # # k## k# # k k k k ## k# k k k k# Nitrate, mg/L # # # !## k#k #k# k # k # # k#k k# k k# k k k# k# k# k k k# kk ! k ! k ## # #kk#k # # k# k# k #k#k# # # k # k # k !k # # NO3 k# k # k#k k! k k k ## k! ! k !#k#k#k Nitrate, mg/L # k # !# kk# # # ## k # # # k#k k k# # k k# k # kk k#k k k# # #k k k##kk# #k # k k k k ! #k k #k # # # ! # k# k## k!# k k#k# kk# !!k## ## k k #k #k# # NO3 0.0 - 2.0 ! k # k #k # k#!# k# !k# k## # k k ! # ! k !#k#k# # #k k# # # k ## ! !k# # # k # ! k#k kkk #k#k#k #k !k # # ! k k k ! # # # #! # kk # !# k#!! k# # !!k# # # k k ## k# 2.10.0 - 10.02.0 ! k !k k # k ! ! kk# !k# k # # # k ! # ##k ! !k # # ! k# k !k kk !k # k # ! !k k k # #k # # ! ! ! k # # k ! k k k k# ! k# k #!! # # # k # # ! k ! 2.1 - 10.0 ! !k # k#k kk# #k# # ## ! # 10.1 - 33.5 ## #k ! !k ! k k# ! # k#!k#k k k# #k k # # ! k# ! !!k !! k # # k k # ! ! ! ! k k k k #k k# kkk# # k # # k # k 10.1 - 33.5 # ! ! k k# k# k k# k k k ! # ! ! !k#k #k !k# k# k k #k # # k# k k # k# k # k k k # # ! ! # k# k# k# # # k k k k #k ! k k k# !k # # k k# ! k# k k # k ! ## k # ! ! #k !k# k # k # kk k # k#k # k # ! k #k k k# kk##k k k kk k# # k k !# k # k##k# k# Of 893 wells ! # k# k#k k kk#k# # kk# # # ## # # # # ! k k k # ! ! ! !#k#k## # k# #k # # k k# # # k ! # # # # k#k k k # k k k#kk # k # #k k k ! #k## # # ! # # !#k k#k kk# ! !!k# # # k ### # # # # tested, 14 % ! k k # ! k#! !k#k k # k#k k!k#!k ## #k # ! # k # # k# k kk # !k #! # ! kk# k # # !k# ! k k #!k! !## #k# # # k k k !k # #!k k # k # # # # k#k !# k kk# ## ! # k # exceed the #k ! !k ! k !k k ! # # kk k k# # ##k# k# #! ! !k# ! ! k k k # k# k # # ! ! kk ! k ! # !k # #k # k## # # !# k # # k ! k # k# k ! k# k # # kkk k # # #k# # !k !# ! k # # ! # # # # k# drinking water ! k #k k # k# k # # k # # k kk ! k k kk # # # ! k k# k!k # #!k# kk k # k### k !k k## k! !k# !#k k k # ! # # # # k ### ## ! k # k k # # ! # # # !# #k k# # standard for # # # k k k k k # # ## k# # # # k k ## kk # k #k k# !k ! #!k# #kk k### k k k## k !# k k # k # # ! k # # !# k # ## # ! k k k k k k # ! k ##!#kk### # ! ! # # k ! # # # # k k k##k# k## k### ! nitrate. 46 % ## kk # !k k k ! ! k # ! ! #k # # #k # k ! k# k k # kk# # k # ! # # ! # k #kk !kk ! # ! k #k k # # ! ! # ! # ! k# k # k # k# #k k# ! # k k#k ! k #kk! k!k# ##k# ## # k #### #!k exceed natural ! k k# k k k! # kk ! !# !k! k !k # # # ! !k# ! k # k #kk ! ! k# k k# ! # #k k# k# k # k !k # # # # k# !!k# !# k kk #k # # # ## # k k #! !k# k#k !# !# ! !k #k# ! nitrate # # k k k ! # k k# # # # k# kk kkk## k # k k !k# !!k# k k# # # # # k k ! # !k## # k# k k ! # !# k ! # # # # k k # kkk## ! k # k k # ! # # concentrations. k k k k # # # k k# !k #!k# k # k### k k k## k ! k # # # k ## # k # !# # # # k # k#k # ## kk # ! # Data from Central ! k # ! k #k # ! ! # k k ## k # k# # ! k ! k # ! ! k # # k # k Wisconsin ! k# k ! k # ! # k kk ! ! k# k# # kk # # ## # k k ! !# ! !k ! Groundwater Center # k ! k k# # # k k# !!k# k # # # !k# k# ! and UW Extension. k # k k kkk## k k ! k# # In summary, Iowa County’s groundwater is abundant but very susceptible to contamination.

The unique geology results in two aquifers separated by an aquifer. This layered system gives rise to many springs and streams in Iowa County.

Questions?

24 The depth to water is shallow in valleys.

5 50 – 20 ft 4 4 3 20 - 50 ft 350 - 100 ft 2 2 100 - 200 ft 1 1> 200 ft

0 1 0 21 2 4 4 ± ± MilesMiles