The implemented tools cover a variety of groundwater-related issues that can be evaluated using analytical equations:

### Groundwater mounding

For surface infiltration systems, the analytical Hantush equation (Hantush, 1967) is used to calculate the groundwater mounding underneath an infiltration basin depending on the recharge rate and duration of recharge, the infiltration basin size, and aquifer parameters such as the initial groundwater level, the specific yield and the hydraulic conductivity. Read more.

### Simple saltwater intrusion equations

Simple saltwater intrusion equations help to assess the location of the freshwater-saltwater interface in coastal aquifers. The main tool is divided into five sub-tools and is used for the calculation of the following parameters: a) Location of the freshwater – saltwater interface under static hydraulic conditions; b) Shape and extent of the freshwater – saltwater interface taking into account the freshwater gradient; c) Upconing of saltwater as a function of well pumping in a saline aquifer overlain by a freshwater lens (including the maximum well pumping rate); d) Critical well discharge creating saltwater intrusion inland; e) Effect of sea level rise on the migration of freshwater – saltwater interface Read more.

### Pumping-induced river drawdown

Pumping from wells located near streams (also referred to as induced riverbank filtration) lowers the groundwater level and reduces surface water flow within the stream, if hydraulically connected. Different analytical equations are applied to calculate the depletion rate for three different boundary conditions, considering the stream’s level of penetration (fully of partially penetrating), and whether streambed resistance is present. Read more.

### Travel time through unconfined aquifer

Travel times and capture zones are essential parameters used to delineate groundwater and wellhead protection zones and to design groundwater remediation systems. The travel time through an unconfined aquifer under selected boundary conditions is calculated for steady-state, saturated flow systems with a one dimensional horizontal flow according to the Dupuit approximation. The unconfined aquifer is recharged by constant surface infiltration and discharges to a fixed-head boundary condition while the bottom layer is impervious. The system is bound by four different options of boundary conditions (constant head boundary conditions, no flow boundaries or pumping wells) and a mechanism is provided to help selecting the correct set of boundaries. Read more.

### One-dimensional transport equation

Knowledge about contaminant behaviour along groundwater flow is important for groundwater quality assessment, especially aquifer storage, transfer and recovery (ASTR) applications. The analytical solution of the advection-dispersion equation helps helps to determine the concentration of a contaminant down-gradient from a constant source, at a given distance and time in a homogeneous, isotropic and porous aquifer with a constant velocity along the flow direction. Read more.

### GIS multi-criteria decision analysis

Suitability maps are increasingly used for MAR planning, specifically for assessing the feasibility of a site for a MAR project. A comprehensive approach for MAR mapping comprises GIS criteria selection, constraint mapping, suitability mapping which includes criteria standardization and weighting as well as combination of standardized criteria and weights by decision rule. The implemented workflow includes several options for criteria weight assignment and decision rules. Read more.

### Quantitative microbial risk assessment

The tool helps to quantify the pathogen occurrence in source water and their removal by various treatment steps at MAR facilities by using a probabilistic approach. The interactive web-based QMRA tool supports the evidence-based risk assessment to minimize water-related infectious diseases.

### Groundwater residence time

Subsurface travel time from the area of recharge to the point of abstraction during MAR is a critical parameter to ensure sufficient attenuation for hygienic parameters and other undesired substances. This tool helps to determine groundwater hydraulic residence time (HRT) using seasonal temperature fluctuations observed in recharge water and MAR recovery wells. This tool represents a proxy for quick, cost-effective and reliable control of travel time during aquifer passage.

### Real-time monitoring

This tool encompasses a web-based monitoring system developed to integrate time series data into the INOWAS platform. Real-time sensors can be connected to the INOWAS platform and time series data can be uploaded. The data can be visualized, processed, downloaded and prepared for further usage,  e.g. as a boundary or observation point in a real-time groundwater flow model.