Aquifers in Alluvial Sediment. Unconsolidated sands and gravels deposited by rivers. Must be large enough to produce significant rates and volumes of water from wells. River valley draining glaciated area Fault bounded basins Partially dissected alluvial plain (High Plains)
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Unconsolidated sands and gravels deposited by rivers. Must be large enough to produce significant rates and volumes of water from wells
Alluvial aquifers in glacial deposits Sediments
Large Glacial Lakes Sediments
Gravel lens within a silty-clay till Sediments
Length: many km
Width: 0.1-several km
Thickness: 0.01-0.1 km
10s km horizontally
Thickness: 0.01-0.1 km
Confining unit where fine grained Sediments
Sand and gravel,
Channel fill in modern valley
Estimate how K varies with depth in alluvial aquifers?
Straight line on log*log plot
Hazen method K=C1d102
Infiltration through floodplain Sediments
Stormflow off uplands
Recharge to alluvial aquifers
Irrigation return flow Sediments
Rise in river stage,
Rise in river stage,
Discharge from basement Sediments
Main channel losing due to pumping
Fine-grained seds on streambed
Fine-grained seds in topstratum
Neither gain nor lose
Preliminary interpretations of gw-sw interactions using head contours
140 miles Sediments20 miles
Fox-Wolf River Basin
Buried pre-glacial valley, now covered by till and lacustrine deposits
Regional GW flow patterns?
Where are thr recharge and discharge areas? What controls?
GW discharge area?
Composition of GW and SW similar
Flow-through lake sandstones, and discharge to river
Cape Cod Bay
Groundwater Flow Paths
Chemung river valley, Corning, NY sandstones, and discharge to river
Limestone and shale bedrock on rounded hills 800 ft or more above the sand and gravel aquifer on the valley floor.
1 mile sandstones, and discharge to river
4000 sandstones, and discharge to river
1:40 aspect ratio
A. sandstones, and discharge to river
Corning Aquifer Exercise
0.6Recharge is from uplands
Water Balance from Conceptual Model
Recharge = Infiltration + Upland Runoff
From map, P = 40 inch/yr, so Re=50 in/yr
Hardness = 2.5 Ca(mg/l) + 4.1 Mg(mg/l) sandstones, and discharge to river
<60 mg/l = soft
>150 mg/l = very hard
Water is magnesium bicarbonate type. Note the hardness. The region is underlain by limestone and shale
16 Mgpd sandstones, and discharge to river
Fine-grained marine sediments underlie glacial outwash in the Little Androscoggin aquifer in Maine.
Glacial valley partially inundated by the sea the Little Androscoggin aquifer in Maine.
5000 ft the Little Androscoggin aquifer in Maine.
P=43 in/yr, ET=23 in/yr (0.53), Ru=20in/yr (0.46)
Also given: Recharge as infiltration over 16 mi2 aquifer accounts for 16.4 cfs, overland from uplands 11.2 cfs, from river 1.4 cfs. 29 cfs total Re to aquifer
Area of aquifer = 16 mi2
Total Recharge=baseflow= 29 cfs: over 16 mi2= 24 in/yr
20 in/yr= 24 in/yr+Stormflow, Negative stormflow?? Problem
Watershed Balance: P+OU=ET+Ru different from above
Infiltration = 16.4 cfs; convert to flux over aquifer: 14 in/yr
Overland from Upland= 11.2 cfs; 9 in/yr
Total Recharge=baseflow= 29 cfs: 24 in/yr
Ru=P+OU-ET=43+9-23=29 in/yr different from above
Ru=Base+Storm, So, stormflow must be 5 in/yr;
In general, the water flux values seem to be inconsistent. Always make certain your water balances can be closed.
Hydraulic head in glacial outwash, Little Androscoggin Aquifer, Maine
7 Mgpd production Aquifer, Maine
4 miles Aquifer, Maine
Aquifer filling a valley once occupied by fresh water glacial lake
Structural Contours on Bedrock Aquifer, Maine
4.3 Mgpd Aquifer, Maine
Little Androscoggin, Na, K, Ca, HCO3;
TDS 67-128 ppm
Irondogenesee Aquifer, Ca, Na, HCO3, Cl, SO4; TDS 665, Hardness: 373
Dissolution of underlying evaporites forms deep troughs in Pecos River Basin
80 Mgpd in Pecos River Basin
Water Quality: 1000+ mg/L common due to underlying evaporites and recharge from saline surface water and irrigation return flow where evaporation has increased salt content