diff --git a/swash/processing/sws_npz.py b/swash/processing/sws_npz.py
index b8c7e1e..c79d4c5 100644
--- a/swash/processing/sws_npz.py
+++ b/swash/processing/sws_npz.py
@@ -32,6 +32,12 @@ botl = read_nohead_scalar(sws_out.joinpath("botl.dat"), n_x)[0, :]
 dep = np.maximum(0, read_nohead_scalar(sws_out.joinpath("dep.dat"), n_x))
 vel = read_nohead_vect(sws_out.joinpath("vel.dat"), n_x)
 
+dt = config.getfloat("post", "dt")
+n_t = botl.shape[0]
+t = np.arange(0, n_t * dt, dt)
+
 log.info(f"Writing npz file in '{inp}'")
 inp.mkdir(exist_ok=True)
-np.savez_compressed(inp.joinpath("sws"), botl=botl, dep=dep, vel=vel)
+np.savez_compressed(
+    inp.joinpath("sws"), x=bathy.index, t=t, botl=botl, dep=dep, vel=vel
+)