# 	**Example 2.9: Baseflow Recession**

#--Part A: Recession constant
Qo = 3500 ft^3/s
t = 100 days
Q = 1500 ft^3/s
a = (-1/t)*ln(Q/Qo); /days 	#Fetter: 8.47e-3 1/days

#--Part B: Base flow after 40 days
t = 40 days
Q = Qo * exp(-a*t); ft^3/s 	#Fetter: 2500 ft^3/s


# 	**Example 2.12.1: Groundwater Recharge**

#--Step 1: Potential groundwater discharge, beginning first year
Qo_first_year = 760 m^3/s
days_per_month = 30 days
To = 6.3 * days_per_month
Vtp_first_year = Qo_first_year * To / 2.3026 	#Fetter: 5.4e9 m^3

#--Step 2: Remaining potential discharge, end of first year
Tend = 7.5 * days_per_month
Vt_end_first_year = Vtp_first_year / 10^(Tend/To) 	#Fetter: 3.5e8 m^3

#--Step 3: Potential groundwater discharge, beginning of second  year
Qo_second_year = 1000 m^3/s
Vtp_second_year = Qo_second_year * To / 2.3026 	#Fetter: 7.1e9 m^3

#--Step 4: Groundwater recharge
Recharge = Vtp_second_year - Vt_end_first_year 	#Fetter: 6.8e9 m^3


# 	**Example 2.12.2: Recharge of Single Event**

#--Step 1: Time of end of overland flow
#--Note:  First make Eqn. 2.5 dimensionally consistent: D = k*A^0.2, where 
#  k = 1.0 and 
#  [units of k] = [units of D] / ([units of A]^0.2) 
#               = days/miles^0.4
Abasin = 235 mile^2
k = 1.0 days/mile^0.4
Dend = k*Abasin^0.2; day 	#Fetter: 2.98 days

#--Step 2: Compute critical time
t1 = 45 days
tc = 0.2144*t1; days 	#Fetter: 9.65 days

#--Step 3: Calculate G=Gw from Eqn. 2.12
Qa = 5 ft^3/s
Qb = 23 ft^3/s
Gw = 2*(Qb-Qa)*t1/2.3026; ft^3 	#Fetter: 6.08e7 ft^3

#--Step 4: Determine depth of recharge
depth = Gw/Abasin; ft 	#Fetter: 0.00928 ft


# 	**Example 2.14: Stream Discharge**

#--Step 1: Calculate velocity
#--Note:  First make Eqn. 2.18B dimensionally consistent: V = (k/n)*R^(2/3)*S^(1/2) where 
#  k = 1.0 and 
#  [units of k] = [units of V]*[units of n] / (([units of R]^(2/3))*)[units of S]^(1/2)) 
#               = m / s m^(2/3) = m^(1/3)/s
Wp = 3.5 ft + 1.5 ft + 1.5 ft
Wp = 6.5 ft
Area = 3.5 ft * 1.5 ft
R = Area/Wp; ft 	#Fetter: 0.808 ft
S = 1.5/500
k = 1.0 m^(1/3)/s
n = 0.012
Vel = k*R^(2/3)*S^(1/2)/n; ft/s 	#Fetter: 5.9 ft/s
Q = Vel*Area; ft^3/s 	#Fetter: 31.0 ft^3/s



# Homework Problems:

TBD