Kerentanan Air Tanah di Kawasan Pertanian Garam Pesisir Pademawu, Madura berdasarkan Karakteristik Hidrogeokimia dan Indeks Kualitas Air

Kawasan pesisir Pademawu yang beralih fungsi menjadi pusat pertanian garam menimbulkan beberapa dampak negatif yang salah satunya adalah permasalahan kerentanan sumber daya air tanah. Beberapa sumur gali milik penduduk sudah berubah menjadi payau hingga asin. Evaluasi terhadap kualitas air tanah di kawasan tersebut sangat dibutuhkan untuk mengetahui kerentanan air tanah. Penilaian kerentanan air tanah dilakukan berdasarkan parameter hidrogeokimia dan indeks kualitas air Water Quality Index (WQI). Fasies hidrokimia air tanah didominasi oleh fasies CaHCO 3 kemudian NaHCO 3 dan NaCl. Nilai rasio Na/Cl dan Cl/HCO 3 menunjukkan bahwa dalam air tanah daerah penelitian telah terjadi proses pencampuran air laut ke dalam akuifer dengan kategori penyusupan air laut sedikit hingga agak tinggi. Diinterpretasikan kondisi tersebut didominasi oleh proses infiltrasi air tambak garam ke dalam akuifer. Nilai Water Quality Index (WQI) berkisar 46,69-736,42, kategori WQI good water mendominasi wilayah penelitian sebanyak 45,45%, excellent 27,28%, poor water 18,18% dan satu sampel air masuk kategori 9,09%. Lokasi dengan kategori poor water dan very poor water berada di sumur gali penduduk yang berdekatan dengan garis pantai dan tambak garam. Pengaturan tataguna lahan antara kawasan pemukiman dan tambak garam sangat dibutuhkan sehingga tidak memperluas area kerentanan air tanah di pesisir Pademawu. Pademawu coastal area has changed  into a center for salt farmin that caused some  negative impacts to groundwater resources. Some dug wells in this area has been reported to produce brackish and salty. Groundwater vulnerability assessment based on hydrogeochemical parameters and Water Quality Index (WQI) have been conducted to identify the vulnerability index. Hydrochemical facies of groundwater is dominated by CaHCO 3 , NaHCO 3 , and NaCl. Ratios of Na / Cl and Cl / HCO 3 show that the in the study area a mixture of sea water within aquifers has bene occurred and categorized as low and slightly high seawater intrusion. This may have been caused by the process of salt-pond water infiltration within aquifers. The WQI is ranged from 46.69-736.42, the category of good water WQI dominates the study area as much as 45.45%, excellent 27.28%, poor water 18.18% and one of water samples reached 9.09%. Categories of poor and very poor water are observed in the wells of residents around the coastline and salt ponds. Land-use reorganizing between residential areas and salt ponds is urgently essential to minimalize the vulnerable area of groundwater in the Pademawu coast.