Source code for groundwater
# -*- coding: utf-8 -*-
# =============================================================================
# This file is part of WaterGAP.
# WaterGAP is an opensource software which computes water flows and storages as
# well as water withdrawals and consumptive uses on all continents.
# You should have received a copy of the LGPLv3 License along with WaterGAP.
# if not see <https://www.gnu.org/licenses/lgpl-3.0>
# =============================================================================
"""Groundwater balance."""
# =============================================================================
# This module computes groundwater balance, including groundwater storage
# and related fluxes for all grid cells based on section 4.5 of
# (Müller Schmied et al. (2021)).
# The groundwater balance equation is solved analytically for each timestep
# of one day to prevent numerical inaccuracies. This avoids the use of very
# small timesteps which will be computationally expensive and hence lead
# to numerical problems.
# =============================================================================
import numpy as np
from numba import njit
from model.lateralwaterbalance import groundwater_adapt_net_abstraction as \
gw_adapt_netabstr
[docs]
@njit(cache=True)
def groundwater_balance(x, y,
aridity_or_inlandsink, groundwater_storage,
diffuse_gw_recharge,
potential_net_abstraction_gw,
daily_unsatisfied_pot_nas, gw_dis_coeff,
prev_potential_water_withdrawal_sw_irri,
prev_potential_consumptive_use_sw_irri,
frac_irri_returnflow_to_gw,
point_source_recharge=None):
"""
Compute daily groundwater balance including storages and related fluxes.
Parameters
----------
x : int
Latitude index of cell
y : int
Longitude index of cell
aridiity : string
Compute groundwater for "Humid" or "Arid" region
groundwater_storage : float
Daily groundwater storage, Unit: [km^3]
diffuse_gw_recharge : float
Daily difuuse groundwater recharge, Unit: [km^3/day]
potential_net_abstraction_gw : float
Potential net abstraction from groundwater, Unit: [km^3/day]
daily_unsatisfied_pot_nas : float
Daily unsatisfied water use, Unit: [km^3/day]
gw_dis_coeff : float
Groundwater discharge coefficient (=0.01),Eqn 21 Müller Schmied et al. (2021), Unit: [1/day]
prev_potential_water_withdrawal_sw_irri : float
Previous potential water withdrawal from surface water for irrigation, Unit: [km^3/day]
prev_potential_consumptive_use_sw_irri: float
Previous potential consumptive use from irrigation using surface water, Unit: [km^3/day]
point_source_recharge : float
Sum of all point groundwater recharge from surface waterboides in
arid regions, Unit: [km^3/day]
Returns
-------
groundwater_storage : float
Updated daily groundwater storage, Unit: [km^3]
groundwater_discharge : float
Updated daily groundwater discharge, Unit: [km^3/day]
actual_net_abstraction_gw: float
Actual Net abstraction from groundwater, Unit: [km^3/day]
"""
# Index (x, y) to print out varibales of interest
# e.g. if x==65 and y==137: print(prev_gw_storage)
# ======================================
# || groundwaterwater balance ||
# ======================================
# Note components of the waterbalance in Equation 20 of Müller Schmied et
# al. (2021) is calulated as follows.
prev_gw_storage = groundwater_storage
# =========================================================================
# Computing net groundwater recharge (netgw_in [km3]) which is defined as
# diffuse recharge + point source recharge - net abstraction.
# =========================================================================
# Point_source_recharge is only computed for (semi)arid surafce water
# bodies but not for inlank sink or humid regions
if aridity_or_inlandsink == "humid" or \
aridity_or_inlandsink == "inland sink":
point_source_recharge = 0
netgw_in = diffuse_gw_recharge + point_source_recharge
# Update net abstraction from groundwater if there is unsatisfied water use
# from previous time step.
actual_net_abstraction_gw = \
np.where(daily_unsatisfied_pot_nas != 0,
gw_adapt_netabstr.
update_netabs_gw(potential_net_abstraction_gw,
prev_potential_water_withdrawal_sw_irri,
prev_potential_consumptive_use_sw_irri,
daily_unsatisfied_pot_nas,
frac_irri_returnflow_to_gw,
x, y),
potential_net_abstraction_gw)
# Updating net groundwater recharge (netgw_in [km3])
netgw_in = netgw_in - actual_net_abstraction_gw
# =========================================================================
# Computing daily groundwater storage (km3) and discharge(km3/day)
# =========================================================================
# Groundwater balance dS/dt = netgw_in - NAg - k*S is solved analytically
# for each time step of 1 day to prevent numerical inaccuracies.
# See in Equation 20 of Müller Schmied et al. (2021)
current_gw_storage = prev_gw_storage * np.exp(-1 * gw_dis_coeff) +\
(netgw_in/gw_dis_coeff)*(1-np.exp(-1 * gw_dis_coeff))
groundwater_discharge = prev_gw_storage - current_gw_storage + netgw_in
# Recalculate groundwater storage when groundwater discharge=0
# dS/dt = netgw_in - NAg (without k*S) -> S(t) = S(t-1) + netgw_in
current_gw_storage = np.where(groundwater_discharge <= 0,
prev_gw_storage + netgw_in,
current_gw_storage)
groundwater_discharge = np.where(groundwater_discharge <= 0, 0,
groundwater_discharge)
return current_gw_storage, groundwater_discharge, actual_net_abstraction_gw
