Replace non-ASCII characters by ASCII characters in the names of vari…

…ables, structs, functions and macros (#388)

* Replace Greek characters by ASCII characters in Markdown files

* Replace Greek characters by ASCII characters in Julia files

* Replace apostrophe's by quotes in plain text

* Replace subscripts and superscripts with ASCII

* Remove redundant aliases

* Add backticks to format parameters as code

* Update changelog.md

docs/src/changelog.md

@@ -57,6 +57,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Always use fractions for the computation of potential evapotranspiration (interception and
   transpiration) and potential evaporation (open water and soil). Replaced variable
   `et_reftopot` by crop coefficient `kc` (use of `et_reftopot` has been deprecated).
+- For improved code readability it is now discouraged to use non-ASCII characters for the
+  names of variables, structs, functions and macros. Using the non-ASCII character for
+  built-in operators is still allowed. This change in naming convention is now in effect and
+  all invalid uses of non-ASCII characters have been replaced by ASCII equivalents.
 
 ### Added
 - Total water storage as an export variable for `SBM` concept. This is the total water stored

docs/src/index.md

@@ -4,7 +4,7 @@ CurrentModule = Wflow
 
 # About wflow
 
-Wflow is Deltares’ solution for modelling hydrological processes, allowing users to account
+Wflow is Deltares' solution for modelling hydrological processes, allowing users to account
 for precipitation, interception, snow accumulation and melt, evapotranspiration, soil water,
 surface water and groundwater recharge in a fully distributed environment. Successfully
 applied worldwide for analyzing flood hazards, drought, climate change impacts and land use

docs/src/model_docs/lateral/kinwave.md

@@ -16,7 +16,7 @@ where ``Q`` is the surface runoff in the kinematic wave [m``^3``/s], ``x`` is th
 the runoff pathway [m], ``A`` is the cross-section area of the runoff pathway [m``^{2}``],
 ``t`` is the integration timestep [s] and ``\alpha`` and ``\beta`` are coefficients.
 
-These equations are solved with a nonlinear scheme using Newton’s method and can also be
+These equations are solved with a nonlinear scheme using Newton's method and can also be
 iterated depending on the  model space and time resolution. By default, the iterations are
 performed until a stable solution is reached (``\epsilon < 10^{-12}``). For larger models,
 the number of iterations can also be fixed for to a specific sub-timestep (in seconds) for
@@ -176,4 +176,4 @@ zero is applied to the upstream flow `qin`.
 
 ## References
 + Chow, V., Maidment, D. and Mays, L., 1988, Applied Hydrology. McGraw-Hill Book Company,
-  New York.
+  New York.

docs/src/model_docs/lateral/sediment_flux.md

@@ -38,7 +38,7 @@ mobilize 5 classes of sediment:
 where ``CLA``, ``SIL`` and ``SAN`` are the primary clay, silt, sand fractions of the topsoil
 and ``PCL``, ``PSI``, ``PSA``, ``SAG`` and ``LAG`` are the clay, silt, sand, small and large
 aggregates fractions of the detached sediment respectively. The transport capacity of the
-flow using Yalin’s equation with particle differentiation, developed by Foster (1982), is:
+flow using Yalin's equation with particle differentiation, developed by Foster (1982), is:
 ```math
    TC_{i} = (P_{e})_{i}  (S_{g})_{i} \, \rho_{w} \,  g \, d_{i}  V_{*}
 ```
@@ -79,7 +79,7 @@ are much rarer than for soil loss and inland dynamics. The simpler models such a
 default sediment river model uses again the transport capacity of the flow to determine if
 there is erosion or deposition (Neitsch et al., 2011).  A more physics-based approach
 (Partheniades, 1965) to determine river erosion is used by Liu et al. (2018) and in the new
-SWAT’s approach developed by Narasimhan et al. (2017). For wflow\_sediment, the new
+SWAT's approach developed by Narasimhan et al. (2017). For wflow\_sediment, the new
 physics-based model of SWAT was chosen for transport and erosion as it enables the use of
 parameter estimation for erosion of bed and bank of the channel and separates the suspended
 from the bed loads.
@@ -313,7 +313,7 @@ deposited sediment and the river bed/bank erosion.
 As sediments have a higher density than water, moving sediments in water can be deposited in
 the river bed. The deposition process depends on the mass of the sediment, but also on flow
 characteristics such as velocity. In wflow_sediment, as in SWAT, deposition is modelled with
-Einstein’s equation (Neitsch et al, 2011):
+Einstein's equation (Neitsch et al, 2011):
 ```math
    P_{dep}=\left(1-\dfrac{1}{e^{x}}\right)100
 ```
@@ -359,14 +359,14 @@ and shifted to the outlet cell. wflow\_sediment handles the lakes and reservoirs
 cell belongs to a lake/reservoir and is not the outlet then the model assumes that no
 erosion/deposition of sediments is happening and the sediments are only all transported to
 the lake/reservoir outlet. Once the sediments reach the outlet, then sediments are deposited
-in the lake/reservoir according to Camp’s model (1945) (Verstraeten et al, 2000):
+in the lake/reservoir according to Camp's model (1945) (Verstraeten et al, 2000):
 ```math
    TE = \dfrac{\omega_{s}}{u_{cr,res}} = \dfrac{A_{res}}{Q_{out,res}} \omega_{s}
 ```
 where ``TE`` is the trapping efficiency of the lake/reservoir (or the fraction of particles
 trapped), ``\omega_{s}`` is the particle velocity from Stokes (m s``^{-1}``), ``u_{cr,res}``
-is the reservoir’s critical settling velocity (m/s) which is equal to the reservoir’s
-outflow ``Q_{out,res}`` (m``^{3}`` s``^{-1}``) divided by the reservoir’s surface area
+is the reservoir's critical settling velocity (m/s) which is equal to the reservoir's
+outflow ``Q_{out,res}`` (m``^{3}`` s``^{-1}``) divided by the reservoir's surface area
 ``A_{res}`` (m``^{2}``).
 
 For reservoirs, coarse sediment particles from the bed load are also assumed to be trapped by the
@@ -439,4 +439,4 @@ transport in overland flow.
   the Total Environment, 538:855-875, 2015. 10.1016/j.scitotenv.2015.08.095
 + O. Vigiak, A. Malago, F. Bouraoui, M. Vanmaercke, F. Obreja, J. Poesen, H. Habersack, J.
   Feher, and S. Groselj. Modelling sediment fluxes in the Danube River Basin with SWAT.
-  Science of the Total Environment, 2017. 10.1016/j.scitotenv.2017.04.236
+  Science of the Total Environment, 2017. 10.1016/j.scitotenv.2017.04.236

docs/src/model_docs/params_lateral.md

@@ -13,7 +13,7 @@ internal model parameter `sl`, and is listed in the Table below between parenthe
 
 |  parameter  | description  	  | unit  | default |
 |:--------------- | ------------------| ----- | -------- |
-| `β`             |  constant in Manning's equation | - | - |
+| `beta`             |  constant in Manning's equation | - | - |
 | **`sl`** (`slope`) |  slope       | m m``^{-1}``| - |
 | **`n`**         | Manning's roughness | s m``^{-\frac{1}{3}}``| 0.036 |
 | **`dl`**        |  length      | m     |  -      |
@@ -27,12 +27,12 @@ internal model parameter `sl`, and is listed in the Table below between parenthe
 | `h`             | water level | m | - |
 | `h_av`          | average water level | m | - |
 | **`bankfull_depth`**   | bankfull river depth  | m | 1.0 |
-| `Δt`            | model time step | s | - |
+| `dt`            | model time step | s | - |
 | `its`           | number of fixed iterations | - | - |
 | **`width`**     |  width       | m          | - |
 | `alpha_pow`     | used in the power part of ``\alpha`` | - | - |
 | `alpha_term`    | term used in computation of ``\alpha`` | - | - |
-| `α`             | constant in momentum equation ``A = \alpha Q^{\beta}`` | s``^{\frac{3}{5}}`` m``^{\frac{1}{5}}`` | - |
+| `alpha`             | constant in momentum equation ``A = \alpha Q^{\beta}`` | s``^{\frac{3}{5}}`` m``^{\frac{1}{5}}`` | - |
 | `cel`           | celerity of kinematic wave | m s``^{-1}`` | - |
 | `reservoir_index`   |  map cell to 0 (no reservoir) or i (pick reservoir i in reservoir field) | - | - |
 | `lake_index`   |  map cell to 0 (no lake) or i (pick lake i in lake field) | - | - |
@@ -50,7 +50,7 @@ internal model parameter `sl`, and is listed in the Table below between parenthe
 
 |  parameter  | description  	  | unit  | default |
 |:--------------- | ------------------| ----- | -------- |
-| `β`             |  constant in Manning's equation | - | - |
+| `beta`             |  constant in Manning's equation | - | - |
 | **`sl`** (`slope`) |  slope       | m m``^{-1}``| - |
 | **`n`**         | Manning's roughness | s m``^{-\frac{1}{3}}``| 0.072 |
 | `dl`            |  length      | m     |  -      |
@@ -62,12 +62,12 @@ internal model parameter `sl`, and is listed in the Table below between parenthe
 | `volume`        | kinematic wave volume |m``^3``| - |
 | `h`             | water level | m | - |
 | `h_av`          | average water level | m | - |
-| `Δt`            | model time step | s | - |
+| `dt`            | model time step | s | - |
 | `its`           | number of fixed iterations | - | - |
 | `width`         |  width       | m          | - |
 | `alpha_pow`     | used in the power part of ``\alpha`` | - | - |
 | `alpha_term`    | term used in computation of ``\alpha`` | - | - |
-| `α`             | constant in momentum equation ``A = \alpha Q^{\beta}`` | s``^{\frac{3}{5}}`` m``^{\frac{1}{5}}`` | - |
+| `alpha`             | constant in momentum equation ``A = \alpha Q^{\beta}`` | s``^{\frac{3}{5}}`` m``^{\frac{1}{5}}`` | - |
 | `cel`           | celerity of kinematic wave | m s``^{-1}`` | - |
 | `to_river`      | part of overland flow that flows to the river | m``^3`` s``^{-1}`` | - |
 | `kinwave_it`    | boolean for kinematic wave iterations | - | false |
@@ -98,7 +98,7 @@ locs = "wflow_reservoirlocs"
 | **`targetfullfrac`** | target fraction full (of max storage)| -        | - |
 | **`targetminfrac`** | target minimum full fraction (of max storage) | -  | - |
 | `demandrelease`| minimum (environmental) flow released from reservoir  | m``^3`` s``^{-1}``| - |
-| `Δt`             | model time step     | s | - |
+| `dt`             | model time step     | s | - |
 | `volume`             | volume     | m``^3`` | - |
 | `inflow`             | total inflow into reservoir | m``^3`` | - |
 | `outflow`             | outflow into reservoir | m``^3`` s``^{-1}`` | - |
@@ -141,7 +141,7 @@ between parentheses.
 | **`lowerlake_ind`** (`linkedlakelocs`) | Index of lower lake (linked lakes) | - | 0 |
 | **`sh`** | data for storage curve | - | - |
 | **`hq`** | data rating curve | - | - |
-| `Δt`             | model time step     | s |  - |
+| `dt`             | model time step     | s |  - |
 | `inflow` | total inflow to the lake | m``^3``  | - |
 | `storage` | storage lake | m``^3``  | - |
 | `maxstorage`| maximum storage lake with rating curve type 1 | m``^3``  | - |
@@ -155,19 +155,19 @@ between parentheses.
 The Table below shows the parameters (fields) of struct `LateralSSF`, including a
 description of these parameters, the unit, and default value if applicable. The parameters
 in bold represent model parameters that can be set through static input data (netCDF). The
-soil related parameters `f`, `soilthickness`, `z_exp`, `θₛ` and `θᵣ` are derived from the
+soil related parameters `f`, `soilthickness`, `z_exp`, `theta_s` and `theta_r` are derived from the
 vertical `SBM` concept (including unit conversion for `f`, `z_exp` and `soilthickness`), and
 can be listed in the TOML configuration file under `[input.vertical]`, to map the internal
-model parameter to the external netCDF variable. The internal slope model parameter `βₗ` is
+model parameter to the external netCDF variable. The internal slope model parameter `slope` is
 set through the TOML file as follows:
 
 ```toml
 [input.lateral.land]
 slope = "Slope"
 ```
 
-The parameter `kh₀` is computed by multiplying the vertical hydraulic conductivity at the
-soil surface `kv₀` (including unit conversion) of the vertical `SBM` concept with the
+The parameter `kh_0` is computed by multiplying the vertical hydraulic conductivity at the
+soil surface `kv_0` (including unit conversion) of the vertical `SBM` concept with the
 internal parameter `khfrac` \[-\] (default value of 1.0). The internal model parameter
 `khfrac` is set through the TOML file as follows:
 
@@ -176,34 +176,34 @@ internal parameter `khfrac` \[-\] (default value of 1.0). The internal model par
 ksathorfrac = "KsatHorFrac"
 ```
 
-The `khfrac` parameter compensates for anisotropy, small scale `kv₀` measurements (soil
+The `khfrac` parameter compensates for anisotropy, small scale `kv_0` measurements (soil
 core) that do not represent larger scale hydraulic conductivity, and smaller flow length
 scales (hillslope) in reality, not represented by the model resolution.
 
 For the vertical [SBM](@ref params_sbm) concept different vertical hydraulic conductivity
 depth profiles are possible, and these also determine which `LateralSSF` parameters are used
 including the input requirements for the computation of lateral subsurface flow. For the
-`exponential` profile the model parameters `kh₀` and `f` are used. For the
-`exponential_constant` profile `kh₀` and `f` are used, and `z_exp` is required as part of
+`exponential` profile the model parameters `kh_0` and `f` are used. For the
+`exponential_constant` profile `kh_0` and `f` are used, and `z_exp` is required as part of
 `[input.vertical]`. For the `layered` profile, `SBM` model parameter `kv` is used, and for
 the `layered_exponential` profile `kv` is used and `z_exp` is required as part of
 `[input.vertical]`.
 
 | parameter | description  	        | unit | default |
 |:---------------| --------------- | ---------------------- | ----- |
-| `kh₀`          | horizontal hydraulic conductivity at soil surface  | m d``^{-1}`` |  3.0 |
-| **`f`** | a scaling parameter (controls exponential decline of `kh₀`) | m``^{-1}``  | 1.0 |
+| `kh_0`          | horizontal hydraulic conductivity at soil surface  | m d``^{-1}`` |  3.0 |
+| **`f`** | a scaling parameter (controls exponential decline of `kh_0`) | m``^{-1}``  | 1.0 |
 | `kh` | horizontal hydraulic conductivity | m d``^{-1}``  | - |
 | **`khfrac`** (`ksathorfrac`) | a muliplication factor applied to vertical hydraulic conductivity `kv` | -  | 100.0 |
 | **`soilthickness`** | soil thickness | m  | 2.0 |
-| **`θₛ`** | saturated water content (porosity) | -  | 0.6 |
-| **`θᵣ`** | residual water content  | -  | 0.01 |
-| `Δt` | model time step | d  | - |
-| **`βₗ`** (`slope`) | slope | m m``^{-1}``  | - |
+| **`theta_s`** | saturated water content (porosity) | -  | 0.6 |
+| **`theta_r`** | residual water content  | -  | 0.01 |
+| `dt` | model time step | d  | - |
+| **`slope`** | slope | m m``^{-1}``  | - |
 | `dl` | drain length | m | - |
 | `dw` | drain width | m | - |
 | `zi` | pseudo-water table depth (top of the saturated zone) | m | - |
-| **`z_exp`** | depth from soil surface for which exponential decline of `kh₀` is valid | m | - |
+| **`z_exp`** | depth from soil surface for which exponential decline of `kh_0` is valid | m | - |
 | `exfiltwater` | exfiltration (groundwater above surface level, saturated excess conditions) | m Δt⁻¹ | - |
 | `recharge` | net recharge to saturated store  | m``^2`` Δt⁻¹ | - |
 | `ssf` | subsurface flow  | m``^3`` d``{-1}``  | - |
@@ -247,18 +247,18 @@ model parameter `mannings_n`, and is listed in the Table below between parenthes
 | `active_n`    |  active nodes | - | - |
 | `active_e`    |  active edges | - | - |
 | `g`    |  acceleration due to gravity | m s``^{-2}`` | - |
-| `α`    |  stability coefficient (Bates et al., 2010) | - | 0.7 |
+| `alpha`    |  stability coefficient (Bates et al., 2010) | - | 0.7 |
 | `h_thresh`    |  depth threshold for calculating flow | m | 0.001 |
-| `Δt`    |  model time step | s | - |
+| `dt`    |  model time step | s | - |
 | `q`    |  river discharge (subgrid channel) | m``^3`` s``^{-1}`` | - |
 | `q_av`    |  average river channel (+ floodplain) discharge | m``^3`` s``^{-1}`` | - |
 | `q_channel_av` | average river channel discharge | m``^3`` s``^{-1}`` | - |
 | `zb_max`    | maximum channel bed elevation | m | - |
 | `mannings_n_sq` | Manning's roughness squared at edge/link | (s m``^{-\frac{1}{3}}``)``^2`` | - |
 | `h`    | water depth | m | - |
-| `η_max`    | maximum water elevation | m | - |
-| `η_src`    | water elevation of source node of edge | m | - |
-| `η_dst`    | water elevation of downstream node of edge | m | - |
+| `zs_max`    | maximum water elevation | m | - |
+| `zs_src`    | water elevation of source node of edge | m | - |
+| `zs_dst`    | water elevation of downstream node of edge | m | - |
 | `hf`    | water depth at edge/link | m | - |
 | `h_av`    | average water depth | m | - |
 | `dl`    | river length | m | - |
@@ -356,10 +356,10 @@ internal model parameter `z`, and is listed in the Table below between parenthes
 | `xwidth`| effective flow width x direction (floodplain) | m | - |
 | `ywidth`| effective flow width y direction (floodplain) | m | - |
 | `g` | acceleration due to gravity | m s``^{-2}`` | - |
-| `θ` | weighting factor (de Almeida et al., 2012) | - | 0.8 |
-| `α`    |  stability coefficient (Bates et al., 2010) | - | 0.7 |
+| `theta` | weighting factor (de Almeida et al., 2012) | - | 0.8 |
+| `alpha`    |  stability coefficient (Bates et al., 2010) | - | 0.7 |
 | `h_thresh`    |  depth threshold for calculating flow | m | 0.001 |
-| `Δt`   |  model time step| s | - |
+| `dt`   |  model time step| s | - |
 | `qy0`  |  flow in y direction at previous time step| m``^3`` s``^{-1}`` | - |
 | `qx0`  |  flow in x direction at previous time step| m``^3`` s``^{-1}`` | - |
 | `qx`  |  flow in x direction | m``^3`` s``^{-1}`` | - |
@@ -412,11 +412,11 @@ altitude = "wflow_dem"
 ```
 
 The input parameter `conductivity` (listed under `[input.lateral.subsurface]`) is not equal
-to the internal model parameter `kh₀`, and is listed in the Table below between parentheses.
+to the internal model parameter `kh_0`, and is listed in the Table below between parentheses.
 
 |  parameter  | description  	        | unit  | default |
 |:--------------- | ------------------| ----- | -------|
-| **`kh₀`** (`conductivity`) | horizontal conductivity  | m d``^{-1}``s | - |
+| **`kh_0`** (`conductivity`) | horizontal conductivity  | m d``^{-1}``s | - |
 | **`specific_yield`**    | specific yield  | m m``^{-1}`` | - |
 | **`top`** (`altitude`)  | top groundwater layer  | m | - |
 | `bottom`     | bottom groundwater layer  | m | - |
@@ -592,7 +592,7 @@ slope = "RiverSlope"
 | **`cbagnold`**| Bagnold c coefficient  | - | - |
 | **`ebagnold`**| Bagnold exponent | - | - |
 | `n`             | number of cells     | - |  - |
-| `Δt`             | model time step     | s |  - |
+| `dt`             | model time step     | s |  - |
 | `ak`             | Kodatie coefficient `a`    | - |  - |
 | `bk`             | Kodatie coefficient `b`    | - |  - |
 | `ck`             | Kodatie coefficient `c`    | - |  - |