GEO 360 - Project One - DUE October 16th 23rd(updated)
Hydrologic Mapping: Development of a Conceptual Model
A hypothetical areal study provides the basis for the following problems in which maps will be
prepared to investigate several aspects of the occurrence of ground water and to illustrate problems in
the preparation of maps. The region to be mapped has been glaciated, and the land surface is underlain
by till everywhere except in two stream valleys where sand and gravel overlie the till. These
unconsolidated deposits constitute one unconfined aquifer. They are underlain by limestone in which
the strata are horizontal. The limestone contains ground water confined beneath the till. The
piezometric surface for the limestone aquifer dips toward the south, although this fact is not well
shown by the provided data. The region has a humid climate.
You will be working in groups (note more than three people and no one author projects) on this
project. To ensure that each student participates, you will evaluate your peers with the provided
guidelines (see the end of the handout). I would encourage students to do the assignment themselves
and then compile the information into one group report. Please turn in the peer evaluation form
individually and not with the project.
Data have been collected from 25 wells (Table 1). For wells number 1 and 20, well logs (from the
drillers) are provided (Table 2). You are provided a topographic map and several base maps upon
which you are to prepare the other types of maps. You are also provided information about the wells,
such as elevation of the land surface and depth to the water level (Table 1).
Working in your groups, you have to:
A) Draw two stratigraphic columns: One for well 1 and one for well 20. In addition to the geology,
incorporate the hydrostratigraphy (hydrogeologic information, i.e. water table or potentiometric
surface, color code aquifers and/or aquitards, etc.) (10)
B) Prepare two cross-sections, one along B-B’ (use wells 13, 14, and 17) and one along C-C’ (use 7,
12, 14, and 20) include the geology, hydrostratigraphy, land surface, the water table, the bedrock
surface, and the potentiometric surface. Include a legend. (10)
C) Describe the general geology and topography of the area - use the stratigraphic columns, the crosssections, and the topographic map (Figure 1) as the basis of description. The description focus is on
the whole area not just what is seen from the wells. (5)
D) Prepare a contour map of the bedrock surface. Use Figure 2 as your base map, a 20-ft contour
interval, and include the 1400-ft contour. Table 4 may be useful in your calculations. (6)
Calculate the slope of the bedrock surface (magnitude and direction). (2)
Approximate the depth at which wells 2 and 5 would intersect the bedrock. (2)
E) Prepare an isopach map (contour map displaying unit thickness) of the till. Use Figure 3 as your
base map, a 20-ft contour interval, and include the 60-ft contour. Keep in mind you have more data
available than just the table. (6)
Describe the thickness of the tile in the area. What role do the stream valleys have on the
thickness? (2)
Approximate the thickness of the till at wells 2 and 5 assuming the wells intersected the
bedrock. (2)
F) Prepare a contour map of the water table. Use Figure 4 as your base map, a 20-ft contour interval,
and include the 1480-ft contour. (7)
Draw flowlines (assume homogeneous and isotropic) (2)
Calculate the gradient of the water table. If more than one dominant direction is identified,
provide multiple gradients. (2)
Include a table showing your calculations and data (Tables 3 and 4 may be useful templates,
but please generate your table using a computer). (1)
Describe the relation between the topography of the region and the water table (How does the
water compare to the topography). (2)
Draw a cross-section along A-A’ (use 2, 4, and 8) as an aid in your description. (3)
Explain, in hydrologic terms, why the marshy areas occur at locations indicated in Figure 1. (2)
Which wells did you use in construction of the water table AND why did you use the wells you
used? (1)
G) Prepare a contour map of the potentiometric surface. Use Figure 5 as your base map, a 10-ft
contour interval, and include the 1530-ft contour. (5)
Draw flowlines (assume isotropic homogeneous). (2)
Calculate the gradient of the potentiometric surface. If more than one dominant direction,
provide multiple gradients. (2)
Include a table showing your data and the calculations. (Tables 3 and 4 may be useful
templates, but please generate your table using a computer). (1)
Describe the shape of the potentiometric surface. (2)
Why do you think the potentiometric surface has this shape-What is the potential control? (2)
Which wells did you use in the construction of the potentiometric surface map and why did you
use the wells you did? (1)
H) Prepare a map of the tracts of potential artesian flow (areas where the level of water is above the
surface). Use Figure 6 as your base map, a 2-ft contour interval. Your interval will begin at 0 ft, and
there will be no negative numbers. (4)
How did you decide where the artesian flow might occur? (1)
I) Based upon all of the information presented and created, describe in THREE DETAILED
PARAGRAPHS the hydrogeology of the region. (15)
Additional basemaps are available on-line
Table 1: Record of Wells
Well
Type of
Number
Well
Land Surface
Elevation
ft. AMSL
1
Drilled
1516
2
Dug
1524
3
Drilled
1518
4
Drilled
1503
5
Dug
1494
6
Dug
1492
7
Dug
1504
8
Drilled
1503
9
Dug
1506
10
Dug
1578
11
Drilled
1543
12
Dug
1527
13
Drilled
1514
14
Drilled
1543
15
Dug
1537
16
Drilled
1538
17
Drilled
1511
18
Dug
1504
19
Dug
1486
20
Drilled
1481
21
Dug
1485
22
Dug
1505
23
Dug
1535
24
Drilled
1502
25
Dug
1525
a
Minus indicates feet below land surface
b
Plus indicates feet above land surface
Depth
ft.
102
12
129
117
11
9
8
119
12
21
140
6
132
133
14
124
71
13
9
79
8
9
16
74
14
Depth to
Bedrock
ft.
95
123
111
100
115
118
125
116
63
64
68
Water Level
ft.
-4.1a
-5.4
+3.9b
+16.7
-5.9
-4.1
-3.8
+11.8
-4.9
-14.7
-17.3
-1.6
+7.0
-12.5
-8.1
-10.9
-.03
-5.2
-4.9
+5.2
-3.6
-4.0
-8.8
-1.2
-7.6
Table 2: Logs of Wells
Description
Well 1
Sand, fine to coarse, with thin beds of pebble gravel and layers of hard
silt
Till, hard; cuttings consist of gravel, sand, silt and clay; sandy layer with
water at 37-38 ft.
Limestone, gray medium-hard, fractured
Well 20
Soil, sandy
Gravel, sandy and sand
Sand, fine and silt
Hardpan (till), hard, quicksand at 28-33 ft.
Limerock, gray, easy-drilling; water at 72 and 78 ft.
Table 3: Tabulation Sheet for Water-table data
Well Number
Land Surface Elevation
ft. AMSL
2
5
6
7
9
10
12
15
18
19
21
22
23
Depth to Water
ft. below surface
Table 4: Tabulation Sheet for Water-table data
Well
Land Surface
Depth to
Thickness of
Number
Elevation
Bedrock
Till
ft. AMSL
1
3
4
8
11
13
14
16
17
20
24
ft.
ft.
Bedrock
Surface
Elevation
ft. AMSL
Thickness
(ft.)
Total Depth
(ft.)
21
21
74
95
7
102
1
8
9
46
15
1
9
18
64
79
Water Elevation
ft. AMSL
Depth to
Water
Water
Elevation
ft. above
surface
ft. AMSL
A’
C’
A
B’
B
C
Figure 1: Topographic Map of the ground water study region with cross-sections AA’, BB’, and CC’
identified. Contour lines show land-surface topography, contour interval, 20 ft. Shaded area is
underlain by sand and gravel, and unshaded area by till. Open circles represent dug wells and solid
circles drilled wells, numbers refer to well records in Tables 1 and 2.
Figure 2: Basemap for use to generate a bedrock surface map.
Figure 3: Basemap for use to generate a thickness of till map.
Figure 4: Basemap for use to generate a water-table map.
Figure 5: Basemap for use to a piezometric-surface map.
Figure 6: Basemap for use to identify tracts of potential artesian flow.
Peer Group Evaluation
Name: ________________________________
Group: ________________________________
Project: _______________________________
A. Please provide numerical scores for each of the members of the group, including yourself. When
evaluating the members of the group, consider the following: 1) Did the person attend all of the
class meetings and outside class meetings; 2) Did the person ask relevant questions and make
valuable contributions to discussions that promoted understanding; 3) Did the person contribute
significant ideas to the group product; 4) Did the person conduct the responsibilities of their role
for this project; 5) Did the person demonstrate knowledge of the course material necessary for this
project; 6) Did the person demonstrate good work ethic by doing their fair share of the work in a
timely manner; and 7) Did the person demonstrate respect for other members of the group? Assign
a score from 1 to 5 for each of the seven categories, with a 5 being the highest score. The overall
score is the sum of the seven categories and should be a number between 7 and 35. Remember,
your scores should be based on behavior and contributions, not personalities or relationships.
Name (Role)
Attend.
Discuss
Idea
Role
Knowl.
Work
Ethic
Respect
Overall
1._________________
2._________________
3._________________
4._________________
B. Please provide additional comments about each member of the group. In particular, it is important
to explain very high and very low scores.
1.
2.
3.
C. Acknowledgement of individual(s) who assisted this group in completing the project:
D. My signature below indicates that I have devoted considerable thought and effort to the evaluation
of my peers and that this evaluation has been completed to the best of my knowledge and ability.
Signed:__________________________
Date:______________________