GIS Based Tool for the Landscape Retention Planning

The valorisation procedure was done (Figure 1) in following steps:

1. Selection of Spatial Planning Unit (SPU) – in this case water bodies (as recommended by EU Water Framework Directive) were used.
2. Selection of available indices characterising disposable water resources and retention capacity of SPU.
3. Spatial analysis based on:

• Calculation of mean values of the factor for each SPU e.g. share of forests, mean unitary outflow;
• Valorisation of the factors into three indices (0; 1; 2) where 2 means that implementation of measures for an increase of retention capacity in a SPU is needed, 1 means that increase of retention capacity in a SPU would be beneficial, and 0 means that there is no need to increase the retention capacity;
• Creation of the aggregation map by summary of the indices for SPUs that spatially overlap each other;
• Redistribution of the values on three needs of retention demand:

1. High – development of small retention is very desirable;
2. Medium – development of small retention is beneficiary;
3. Low – development of small retention is not needed.

For example, the indicators listed in Table 1 were defined for the Mazovian Region in Poland, but similar calculations can be done for other regions. 

The aim of this analysis is to increase the flexibility of the spatial planning, defined by the area, not the precise location, and evaluate the investments in the light of environmental needs.

In the first stage of the analysis, a water body was selected as a Spatial Planning Unit (SPU).

In the second stage, considering limitations in data availability, four groups of factors characterising disposable water resources were identified:

Climatic (meteorology and hydrology) indicators:

1. Climatic water balance (difference between precipitation (P) and reference evaporation (ETo));
2. Frequency of precipitation lower than 50% of the mean multiannual value.

Hydrological conditions:

1. Multiannual mean unitary outflow;
2. Ratio of the maximal flow (with probability of 1%) to the mean flow;
3. Flood risk area.

Hydrogeological indicators:

1. Groundwater renewable resources module for first aquifer;
2. Soil water retention (for 1m layer depth and 2-4.2 pF).

Land use indicators from Corin Land Cover (participation in % in SPU):

1. Forests;
2. Lakes and artificial water reservoirs;
3. Urbanised areas;
4. Orchards and vegetable cultivation;
5. Arable lands.

A map of the climatic indicators has been developed based on the interpolation of meteorological data that was obtained from the representative measuring sites (Figure 2a). A map of the hydrologic indicators has been generated by connecting the multiannual statistical data on water flow from water gauges with the respective catchments. A map of the soil retention has been developed by the Polish Institute of Soil Science and Plant Cultivation. Finally, a map of the module of renewable groundwater resources has been obtained from Polish Geological Institute.

In the third stage, the mean value of all indicators for each water body was calculated based on the spatial analysis. The exemplary results of the analysis have been presented in Figure 11a and Figure 11b. In the next step, values of the indicators have been changed into indices: {0; 1; 2} (Figure 2c). The process demanded definition of two threshold values for each indicator. The threshold values defined the degree of needs of the area for development of small retention. The threshold values reflecting respective classes of needs and the scope of variation of the analysed indicators have been given in Table 4. These values should be evaluated individually, depending on the characteristics of the analysed area. In the next step, a summary evaluation of the needs of each water body was done. The evaluation was based on all analysed indicators. Based on the total value of all points (maximum number that was possible to obtain was 17), all Unified Water Bodies (UWB) were grouped into three categories (Figure 3):

• High need of small retention – water bodies with a sum of all points equal or higher than 12 points;
• Medium need of small retention – water bodies with a sum of all points between 7 and 11 points;
• No needs of small retention – water bodies with s sum of all points below 7.