Update app.py with the new formula.

dca-carouge-fountain/app.py

@@ -171,6 +171,7 @@ def get_model_water_quality_observed(
         totalChlorine=None,
         chlorateEstimation=None,
         meta_datetime=None,
+        cl=None,
 ):
     """
     If meta_datetime is provided then all the attrs are assigned meta_datetime as dateModified meta date
@@ -184,6 +185,7 @@ def get_model_water_quality_observed(
     :param totalChlorine:
     :param chlorateEstimation:
     :param meta_datetime:
+    :param cl:
     :return:
 
     comments by IBATECH:
@@ -221,13 +223,18 @@ def get_model_water_quality_observed(
         'totalChlorine',
         'chlorateEstimation',
         'dateObserved',
-        'location'
+        'location',
+        'cl'
     ]
 
     # Handle the timestamp
     meta_datetime = meta_datetime.replace("T", " ")
     meta_datetime = meta_datetime.replace("Z", "")
     
+    if pH is not None:
+        # Calculate CL-
+        cl = 2.41840247818555 - 0.0438725641757871 * pH + 0.670467600246094 * freeChlorine - 0.669365973598627 * totalChlorine - 0.00302592842093426 * redox
+
     for v in values:
         key = v
         val = locals()[v]  # gets var value from var name