def test_lookup_cn(self):
"""
Do some spot-checks on the data from Table C.
"""
self.assertEqual(lookup_cn('a', 'water'), 100)
self.assertEqual(lookup_cn('b', 'li_residential'), 68)
self.assertEqual(lookup_cn('c', 'hi_residential'), 90)
self.assertEqual(lookup_cn('d', 'commercial'), 95)
self.assertEqual(lookup_cn('a', 'rock'), 77)
self.assertEqual(lookup_cn('b', 'deciduous_forest'), 55)
self.assertEqual(lookup_cn('c', 'evergreen_forest'), 70)
self.assertEqual(lookup_cn('d', 'mixed_forest'), 77)
def test_lookup_cn(self):
"""
Do some spot-checks on the data from Table C.
"""
self.assertEqual(lookup_cn('a', 'open_water'), 100)
self.assertEqual(lookup_cn('b', 'developed_low'), 80)
self.assertEqual(lookup_cn('c', 'developed_med'), 91)
self.assertEqual(lookup_cn('d', 'developed_high'), 96)
self.assertEqual(lookup_cn('a', 'barren_land'), 77)
self.assertEqual(lookup_cn('b', 'deciduous_forest'), 55)
self.assertEqual(lookup_cn('c', 'evergreen_forest'), 70)
self.assertEqual(lookup_cn('d', 'mixed_forest'), 77)
def runoff_nrcs(precip, evaptrans, soil_type, land_use):
"""
The runoff equation from the TR-55 document. The output is a
runoff value in inches.
"""
curve_number = lookup_cn(soil_type, land_use)
if nrcs_cutoff(precip, curve_number):
return 0.0
potential_retention = (1000.0 / curve_number) - 10
initial_abs = 0.2 * potential_retention
precip_minus_initial_abs = precip - initial_abs
numerator = pow(precip_minus_initial_abs, 2)
denominator = (precip_minus_initial_abs + potential_retention)
runoff = numerator / denominator
return min(runoff, precip - evaptrans)
def runoff_nrcs(precip, evaptrans, soil_type, land_use):
"""
The runoff equation from the TR-55 document. The output is a
runoff value in inches.
"""
if land_use == 'cluster_housing':
land_use = 'developed_low'
curve_number = lookup_cn(soil_type, land_use)
if nrcs_cutoff(precip, curve_number):
return 0.0
potential_retention = (1000.0 / curve_number) - 10
initial_abs = 0.2 * potential_retention
precip_minus_initial_abs = precip - initial_abs
numerator = pow(precip_minus_initial_abs, 2)
denominator = (precip_minus_initial_abs + potential_retention)
runoff = numerator / denominator
return min(runoff, precip - evaptrans)
