Mean waterlevels cannot be reproduced for old periods

The slotgemiddelden are based on mean water levels, but these cannot be reproduced for old periods because of data gaps.

The data retrieved from the DDL is not complete as documented in https://github.com/Rijkswaterstaat/wm-ws-dl/issues/16, but even when using a validation dia from TK, there are large data gaps for which there are mean waterlevels available in a dataset provided by AB. How were these computed in absence of waterlevel data?

import os
import pandas as pd
import hatyan
import matplotlib.pyplot as plt
plt.close("all")

# read the timeseries provided by TK
dir_data = r"p:\archivedprojects\11208031-010-kenmerkende-waarden-k\work\data_vanRWS_20220805\wetransfer_waterstandsgegevens_2022-08-05_1306"
file_dia_hoek1 = os.path.join(dir_data, r"WATHTE_10min\HOEKVHLD_1.dia")
file_dia_hoek2 = os.path.join(dir_data, r"WATHTE_oud\HOEK_KW.dia")
ts_hoek = hatyan.read_dia([file_dia_hoek1,file_dia_hoek2], block_ids="allstation", station="HOEKVHLD", allow_duplicates=True)

# read the mean water levels provided by AB
file_mean = r"p:\archivedprojects\11208031-010-kenmerkende-waarden-k\work\data_KW-RMM\HOEK_Z.txt"
mean_hw = pd.read_csv(file_mean, sep="\\s+", skiprows=1, names=["datetime","values"])
mean_hw['datetime'] = pd.to_datetime(mean_hw['datetime'].astype(str) +"-01-01")
mean_hw = mean_hw.set_index("datetime")
mean_hw["values"] /= 100

fig,ax = plt.subplots(figsize=(10,5))
ts_hoek["values"].plot(ax=ax, label="tijdreeks")
mean_hw["values"].plot(ax=ax, marker="x", linestyle="", color="r")
ax.set_title("HOEKVHLD")
ax.legend()
ax.grid()
ax.set_xlim(pd.Timestamp("1890-01-01"),pd.Timestamp("2024-01-01"))
fig.tight_layout()

Gives:

Deltares-research / kenmerkendewaarden

Mean waterlevels cannot be reproduced for old periods #105