Will | Python Fiddle

#GDD for only one day
def GDD(tMin,tMax):
   tBase = 15;
   gdd_today = ((tMax + tMin)/2)-tBase;
   if gdd_today < 0 :
       gdd_today = 0;# only values greater than zero are valid
   return (gdd_today);

#convert the Flow rate m3/s of the river to Velocity m/s
#forumula for velocity depends on the location
def velocity(flowrate,location):
   y=-1;#default value for velocity
   if location == 0 :#Krosno Creek
      y = (0.2692*flowrate) + 0.0984;
   if location == 1 :#Spring Creek North
      y = -(0.0288*flowrate*flowrate) + (0.4097*flowrate) + 0.1393;
   if location == 2 :#Don at Glenshields
      y = (0.2717*flowrate) + 0.148;   
   return (y);

#get the spawn length for the fish species
def predicted_spawn_length(species,stream_velocity):
   incubation_period=-1;#default value for velocity
   if species == 0 :#C. idella 
      incubation_period=(233855*stream_velocity**(-2.4915));
   if species == 1 :#H. molitrix y=22456x-2.0989
      incubation_period=(22456*stream_velocity**(-2.0989));
   if species == 2 :#M. piceus 
      incubation_period=(233855*stream_velocity**(-2.822)); 
   spawn_distance=3.6*stream_velocity*(incubation_period*60);#convert incubation period from hours to seconds
   return (spawn_distance);

#get the likelihood for a spawn to form
def spawn_likelihood(gdd_sum,water_temp,predicted_spawn_distance,unimpounded_length,flow_rate):
    if gdd_sum > 650 and water_temp > 17 and unimpounded_length > predicted_spawn_distance and flow_rate > 0.7 and gdd_sum > 900:
          return('Status = Highly Suitable');
    if gdd_sum > 650 and water_temp > 17 and unimpounded_length > predicted_spawn_distance and flow_rate < 0.7 and gdd_sum > 900:
          return('Status = Very Suitable');
    if gdd_sum > 650 and water_temp > 17 and unimpounded_length > predicted_spawn_distance and flow_rate > 0.7 and gdd_sum < 900:
          return('Status = Suitable');
    if gdd_sum > 650 and water_temp > 17 and unimpounded_length > predicted_spawn_distance and flow_rate < 0.7 and gdd_sum < 900:
          return('Status = Minimally Suitable');
    else:
          return('Status = Not Suitable');
            
print (spawn_likelihood(10,22,2,5,700));

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