In our previous study mentioned above we found that the daily dynamics of magnesium were high in Rehovot and Ashkelon (big cities of the Central and South Districts) and were low in Kibbutz Ha-Goshrim (a small settlement in the North District). The stable mineral composition of the tap water points to constant natural water sources, whereas significant daily changes point to mixing water of different quality from several sources. The decrease in tap water hardness is one of the consequences of the intensive use of DSW. According to , after the operation of the Ashkelon plant, the water hardness was measured in the following cities: Beer Sheeba, Kiryat Gat, Ofakim, Sderot, and Netivot, which are downstream of the Ashkelon DSP. It was found that as a result of blending between DSW and water from NWC and local wells, the hardness decreased from 19 to 50% depending on the city and season . Tap water softening has numerous economic benefits, such as extending the lifetime of solar panels, which may save around 60 million USD annually for all of Israel . On the other hand, the lack of important minerals in tap water softened by DSW addition is a public health concern.