Recharge: what, how, where?

http://www.sandia.gov/aqua/images/aquifer.gif

http://www.byways.org/explore/byways/2065/places/30147/photos.html?id=30508andhttp://en.wikipedia.org/wiki/File:Windsurfer_Walchensee.jpg

Jesse RoachApril 9, 2011

“What western U.S. city sits atop anunderground lake superior?”

Some definitions (the what)• Aquifer: Underground geologic unit saturated with water

(with porosity and permeability sufficient for useful extraction)• Water table: top of the saturated zone (point where pressure = atmospheric)• Vadose zone or unsaturated zone: between the land surface and the water table• Infiltration or seepage: movement of water into the subsurface• Recharge: movement of water into the aquifer, ie when it reaches the water table

http://www.co.mchenry.il.us/departments/waterresources/Pages/GroundwaterBasics.aspx

Groundwater movement through an aquifer• Groundwater moves from areas of high water table to lower water table (unconfined

aquifers) in direct relation to the gradient of the water table (Darcy’s law).

• What groundwater lacks in temporal velocity, it makes up in spatial extent

For example, consider gw that moves 1 inch per day in an aquifer 1000 feet thick and 10 miles wide:1 inch/day * 1ft/12inch * 1000 ft * 10 mile * 5280 ft/mile = 4400000 ft3/day = 51 cfs

http://www.umaine.edu/WaterResearch/outreach/groundwater_protection_digest.htm

http://wapi.isu.edu/envgeo/aquifer_gw_review/flownets.htm

Cross section: Plan view:

Storage, recharge, and discharge• Water enters the aquifer via recharge, and leaves the aquifer via discharge.

• The change in aquifer storage in a given amount of time is equal to recharge less discharge in that time (just like your bank account).

• And thus when there is no change in storage (steady state), recharge = discharge

• Long term sustainability of an aquifer requires no negative change in storage over meaningful time periods (also just like your bank account)

DRStorage −=∆

DRStorage =⇒=∆ 0

http://www.answersincreation.org/curriculum/geology/images/Groundwater_flow_times_usgs_cir1139.png

Recharging the bank account (the how):

• Injection wells• Septic tanks

• Mountain front recharge? (via highly preferential fracture flow?)

Localized -point

• Ditches, canals, (drains)• Mountain front recharge• Streams and arroyos

Localized -linear

• Irrigated agriculture• Recharge basins

Rainfall/snowmelt on permeable sediments with shallow water table

Distributed (Areal)

Human causedNaturalRecharge type

Recharging the bank account (the how):

• Injection wells• Mountain front recharge? (via highly preferential fracture flow?)

Localized -point

• Ditches, canals, (drains)• Mountain front recharge• Streams and arroyos

Localized -linear

• Irrigated agriculture• Recharge basins

Rainfall/snowmelt on permeable sediments with shallow water table

Distributed (Areal)

Human causedNaturalRecharge type

http://faculty.kutztown.edu/friehauf/hydrostudies/sourcewater_project.html

Recharging the bank account (the how):

• Injection wells• Mountain front recharge? (via highly preferential fracture flow?)

Localized -point

• Ditches, canals, (drains)• Mountain front recharge• Streams and arroyos

Localized -linear

• Irrigated agriculture• Recharge basins

Rainfall/snowmelt on permeable sediments with shallow water table

Distributed (Areal)

Human causedNaturalRecharge type

http://www.greenfudge.org/2010/08/25/the-water-we-eat-irrigated-agricultures-heavy-toll/

http://www.tucsonweekly.com/tucson/ImageArchives?by=1845300&category=1063731&feature=Stories&section=1063709

Recharging the bank account (the how):

• Injection wells• Mountain front recharge? (via highly preferential fracture flow?)

Localized -point

• Ditches, canals, (drains)• Mountain front recharge• Streams and arroyos

Localized -linear

• Irrigated agriculture• Recharge basins

Rainfall/snowmelt on permeable sediments with shallow water table

Distributed (Areal)

Human causedNaturalRecharge type

http://pubs.usgs.gov/ha/ha730/ch_c/jpeg/C037.jpeg http://www.science-project.com/_members/science-projects/tblib/stream/vms21.html

Recharging the bank account (the how):

• Injection wells• Septic tanks

• Mountain front recharge? (via highly preferential fracture flow?)

Localized -point

• Ditches, canals, (drains)• Mountain front recharge• Streams and arroyos

Localized -linear

• Irrigated agriculture• Recharge basins

Rainfall/snowmelt on permeable sediments with shallow water table

Distributed (Areal)

Human causedNaturalRecharge type

http://www.unep.or.jp/ietc/publications/techpublications/techpub-8a/recharge.asp

http://www.solinst.com/Res/papers/101C4Salt.html

Albuquerque GW basin:

Predevelopment: Steady state, no ag 100’ contours

~1995 conditions: 50’ contours

From McAda and Barroll 2002. SIMULATION OF GROUND-WATER FLOW IN THE MIDDLE RIO GRANDE BASIN BETWEEN COCHITI AND SAN ACACIA, NEW MEXICO

River

Regional Aquifer

WellShallow Aquifer

AgDrain

ETRecharge

Albuquerque basin recharge/dischargeRecharge terms: Mountain front, tributary, and riverDischarge terms: ET, agricultural drains, and wells (until now!)

(River and drain terms depend on sw and gw levels such that either could be a recharge or discharge term in localized areas.)

Recharge in Alb GW basin (the where):From McAda and Barroll 2002

http://nm.water.usgs.gov/publications/abstracts/wrir02-4200.pdf

Predevelopment steady state in kAF/yr:Mountain front recharge: ~ 43Tributary recharge: ~ 9Rio Grande recharge: ~ 63(115 kAF/yr total = 160 cfs)

Current:Mountain front recharge: ~ 43Tributary recharge: ~ 9 Rio Grande recharge: ~ 316Irrigation recharge:~ 35 Ditch recharge:~ 90Drain capture:~ -341(152 kAF/yr total = 210 cfs)

351

441100

Alb GW basin simulated water budgetFr

om M

cAda

and

Bar

roll

2002