This document analyzes water usage and availability over a 10-year period in a tri-county watershed based on population growth projections. It contains 6 tables that provide hydrologic data, population statistics, well usage, and projections. The analysis finds that while population growth will increase water usage, the watershed's natural recharge and river water permits can support the expected population of 599,000 people by 2022 without exceeding limits. River water will need to supplement groundwater in some years but total usage is projected to remain sustainable.
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Lab 7 write up
1. Jordan Sedlock
3/24/15
GEOL 305
Lab #7 Tri-county water management exercise
The current permits for river water withdrawal are still adequate and based on past
history and future projected growth and estimates, this watershed will be able to
support and withstand the population growth that is expected to occur over the next
ten years. A ten-year tri-county hydrologic history can be found in Table 1 below.
Table 1. 10 year hydrologic history of tri-county watershed
Year Rn Qi Qo T Qp S S (pump) From river
2012 6.11E+06 2.09E+04 2.53E+05 1.50E+05 7377562.5 5.73E+06 -1.65E+06 1.65E+06
2011 5.83E+06 2.19E+04 2.42E+05 1.50E+05 7028098.725 5.46E+06 -1.57E+06 1.57E+06
2010 4.72E+06 2.71E+04 1.96E+05 1.50E+05 6678634.95 4.40E+06 -2.28E+06 2.28E+06
2009 5.00E+06 2.56E+04 2.07E+05 1.50E+05 6329171.175 4.67E+06 -1.66E+06 1.66E+06
2008 5.27E+06 2.42E+04 2.19E+05 1.50E+05 5979707.4 4.93E+06 -1.05E+06 1.05E+06
2007 5.83E+06 2.19E+04 2.42E+05 1.50E+05 5630243.625 5.46E+06 -1.70E+05 1.70E+05
2006 5.83E+06 2.19E+04 2.42E+05 1.50E+05 5280779.85 5.46E+06 1.79E+05
2005 6.11E+06 2.09E+04 2.53E+05 1.50E+05 4931316.075 5.73E+06 7.97E+05
2004 5.72E+06 2.23E+04 2.37E+05 1.50E+05 4581852.3 5.36E+06 7.73E+05
2003 5.72E+06 2.23E+04 2.37E+05 1.50E+05 4232388.525 5.36E+06 1.12E+06
2002 5.55E+06 2.30E+04 2.30E+05 1.50E+05 3882924.75 5.19E+06 1.31E+06
Note all units are in m3 water/year
In Table 1, for the years 2007-2012 the population has expanded past the point of
sole dependence on its ground water and in order to balance out the deficit, which
you can see by the negative values of change in ground water storage, S, the
population must draw on the river water supply. This is perfectly acceptable and
does not disrupt the river water supply in any way, as the limit of 5.55 *106 m3/year
is not exceeded. Explanation of final four columns in table to follow.
Table 2 below, contains population and well data useful for calculations and
projections.
Table 2. Data by county in tri-county watershed
County Population Number of
wells
River permit
locations
River water
permit (m3/year)
East River 110,000 27,500 1 3.15E+05
Upgradient 185,000 46,250 2,3 5.10E+05
Downgradient 244,000 61,000 3,4 6.75E+05
Important to note that this data is current as of 2012
2. Jordan Sedlock
3/24/15
GEOL 305
Lab #7 Tri-county water management exercise
Table 3 contains estimates of approximate population data from 2002-2012
knowing that there was a 90% increase in population as well as estimates of
approximate population data for 2013-2022 assuming the population will increase
to 599,000 residents and gain 15,000 more wells.
Table 3. Estimates and Approximations
Year Population # Wells
Qp/year
(m3/year)
2022 599,000 149,750 8198812.5
2021 593,000 148,250 8116687.5
2020 587,000 146,750 8034562.5
2019 581,000 145,250 7952437.5
2018 575,000 143,750 7870312.5
2017 569,000 142,250 7788187.5
2016 563,000 140,750 7706062.5
2015 557,000 139,250 7623937.5
2014 551,000 137,750 7541812.5
2013 545,000 136,250 7459687.5
2012 539,000 134,750 7377562.5
2011 513,468 128,367.1 7028098.725
2010 487,937 121,984.2 6678634.95
2009 462,405 115,601.3 6329171.175
2008 436,874 109,218.4 5979707.4
2007 411,342 102,835.5 5630243.625
2006 385,810 96,452.6 5280779.85
2005 360,279 90,069.7 4931316.075
2004 334,747 83,686.8 4581852.3
2003 309,216 77,303.9 4232388.525
2002 283,684 70,921 3882924.75
From 2002-2012, as the population expanded, so did the number of wells available
to be drawn from. Qp (Table 1) was found by multiplying the pump per year of 54.75
m3/year by the number of wells assumed to have existed each year. The number of
wells each year was found by dividing the assumed population each year by 4 (Table
2). It was assumed that for every 4 people, one well existed (found by dividing the
population by number of wells that existed). Once Qp was calculated, S was found
by plugging each variable into the following equation: RN+Qi Qo T Qp = S.
Youll notice two difference S values, one that includes the pump of residents
drawing their water supply from wells (S with pump) and one that does not
include the pump but represents the natural order of the hydrologic cycle (S). As
previously stated, in years with a negative value for S, the water was then drawn
from the river water supply.
3. Jordan Sedlock
3/24/15
GEOL 305
Lab #7 Tri-county water management exercise
With anticipated population growth, projected pumping (Qp) and change in ground
water storage (S) can be determined in the same manner as previously discussed.
Table 3 shows all expected and extrapolated data calculated for population per year,
wells per year, and anticipated pump per year based on population per year. Using
the range of residents in the total population, estimates of population per year were
calculated. The number of wells was calculated in the same way as previously
described and projected Qp values were calculated in the same way as previously
described. These are all based on the assumption that population will increase as
projected, however, this may not necessarily be the case, i.e., population could
increase faster, or slower, or there could be more residents or less residents than
anticipated.
In order to project a value for change in ground water storage, an average for the
following was calculated, RN, Qi, and Qo (Table 4). These values were calculated
using the data from Table 1.
Table 4. Calculated values of recharge
and discharge
AVG Rn min max
5.61E+06 4.72E+06 6.11E+06
AVG Qi min max
2.29E+04 2.09E+04 2.71E+04
AVG Qo min max
2.33E+05 1.96E+05 2.53E+05
Note all units in m3 water/year
Plugging these new values into the formerly mentioned equation, RN+Qi Qo T
Qp = S, two cases of S were calculated, a low recharge (incorporating the
minimum values in Table 4) case and a high recharge case (incorporating the
maximum values in Table 4) which can be found in Table 5 below.
Table 5. Calculated values of
low and high recharge to the
hydrologic cycle
Low recharge High recharge
4.74E+06 6.14E+06
Note all units in m3 water/year
The above values are representative of only the first three variables in the same
equation that has been used. Considering each case individually, using the low
recharge value in Table 5, the same value of T in Table 1, and the calculated value of
Qp for 2022 in Table 3, a lower S was calculated (Table 6). Using the high recharge
4. Jordan Sedlock
3/24/15
GEOL 305
Lab #7 Tri-county water management exercise
value in Table 5, the same value of T in Table 1, and the calculated value of Qp for
2022 in Table 3, a higher S was calculated (Table 6).
Table 6. Projected S & river water withdrawals
Wells From River
Low S High S High case Low case
-3.80E+06 -2.24E+06 3.80E+06 2.24E+06
Note all units in m3 water/year
Table 6 also contains projected river water withdrawals that will be needed based
on the deficit that is seen when the population depends solely on well water. In both
cases, drawing on the river water supply will be necessary and in both cases,
drawing on the river water supply will be feasible and allowable, as the limit of
5.55*106 m3water/year is not exceeded. Based on all of my calculations and
projections, this watershed will be able to support the expected population growth
over the next ten years.