diff --git a/olaflow/processing/sws_ola.py b/olaflow/processing/sws_ola.py
index f0083e2..0eb4ddb 100644
--- a/olaflow/processing/sws_ola.py
+++ b/olaflow/processing/sws_ola.py
@@ -32,6 +32,8 @@ of_x, of_y, of_z = mesh = readof.readmesh(str(olaflow_root))
 
 watl = interpolate.interp1d(x, sws["watl"][680])
 
+alpha_water = np.where(of_z < watl(of_x), "1", "0")
+
 with open(olaflow_root.joinpath("0", "alpha.water"), "r") as aw_file:
     aw_raw = aw_file.read()
 
@@ -39,7 +41,7 @@ with open(olaflow_root.joinpath("0", "alpha.water"), "w") as aw_file:
     aw_file.write(
         re.sub(
             r"(?<=\(\n).*?(?=\n\))",
-            "\n".join(map(str, alpha_water)),
+            "\n".join(alpha_water),
             aw_raw,
             count=1,
             flags=re.S,