Sustainable Management of the Salalah Coastal Aquifer, Oman

SUSTAINABLE MANAGEMENT OF THE SALALAH COASTAL AQUIFER IN OMAN USING AN INTEGRATED APPROACH

Mahaad Issa Shammas

May 2007

TRITA-LWR PhD Thesis 1031 ISSN 1650-8602 ISRN KTH/LWR/PHD 1031-SE ISBN 978-91-7178-645-6 Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

Cover Illustration:

Satellite image of Salalah plain and adjacent Jabal Al-Qara (source, National Meteorological Service/Sultanate of Oman, 2004).

Doctoral Thesis Department of Land and Water Resources Engineering Royal Institute of Technology (KTH) SE-100 44 STOCKHOLM, Sweden

TRITA-LWR PhD Thesis 1031 ISSN 1650-8602 ISRN KTH/LWR/PHD 1031-SE

ISBN 978-91-7178-645-6 Universitetsservice US AB, Stockholm, 2007

ii Mahaad Shammas TRITA LWR PhD Thesis 1031

I dedicate this work to my elder brother Ali, with love

iii Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

iv Mahaad Shammas TRITA LWR PhD Thesis 1031

ﺑﺴﻢ اﷲ اﻟﺮﺣﻤﻦ اﻟﺮﺣﻴﻢ

اﻹدارة اﻟﻤﺴﺘﺪاﻣﺔ ﻟﺤﻮض ﺳﻬﻞ ﺻﻼﻟﺔ اﻟﺠﻮﻓﻲ اﻟﺴﺎﺣﻠﻲ ﺑﺎﺳﺘﺨﺪام ﻧﻤﻮذج ﻣﺘﻜﺎﻣﻞ (ﻣﻠﺨﺺ ) ) ﺗﻜﻮن ﺣﻮض ﺳﻬﻞ ﺻﻼﻟﺔ اﻟﺠﻮﻓﻲ اﻟﺴﺎﺣﻠﻲ اﻟﻀﺤﻞ ﻓﻲ ﻃﺒﻘﺎت ﻣﻦ اﻟﺤﺠﺮ اﻟﺠﻴﺮي اﻟﺜﻼﺛﻲ، ﻳﻤﺘﺪ ﺷ ﻤ ﺎ ﻻً إﻟﻰ أﻗﺪام ﺟﺒﺎل اﻟﻘﺮا وﺟﻨﻮﺑﺎً إﻟﻰ ﺷﺎﻃﺊ اﻟﺤﺎﻓﺔ . ﺗﻌﻠﻮ ﻃﺒﻘﺔ اﻟﺤﺠﺮ اﻟﺠﻴﺮي ﻃﺒﻘﺔ ﻣﻦ رﺳﻮﺑﻴﺎت اﻟﻌﺼﺮ اﻟﺮﺑﺎﻋﻲ، ﺗﺘﻜﻮن ﻣﻦ رﺳﻮﺑﻴﺎت اﻷودﻳﺔ اﻟﻐﺮﻳﻨﻴﺔ واﻟﺮﺳﻮﺑﻴﺎت اﻟﺠﻴﺮﻳﺔ اﻟﺴﺎﺣﻠﻴﺔ . ﺗﻄﻮرت ﻋﺪﺳﺔ ﻋﺬﺑﺔ ﻣﻦ اﻟﻤﻴﺎﻩ اﻟﺠﻮﻓﻴﺔ ﻓﻲ وﺳﻂ اﻟﺴﻬﻞ ﻣﻊ وﺟﻮد ﻣﻴﺎﻩ ﺟﻮﻓﻴﺔ ﺷﺒﺔ ﻣﺎﻟﺤﺔ إﻟﻰ اﻟﺸﺮق واﻟﻐﺮب ﻣﻦ اﻟﺴﻬﻞ ﺑﻴﻨﻤﺎ ﺗﺤﺪث ﻋﻤﻠﻴﺔ ﺗﺪاﺧﻞ ﻟﻤﻴﺎﻩ اﻟﺒﺤﺮ ﻣﻦ ﺟﻬﺔ اﻟﺠﻨﻮب . ﺗﻢ دراﺳﺔ اﻹدارة اﻟﻤﺴﺘﺪاﻣﺔ ﻟﻠﻤﻴﺎﻩ اﻟﺠﻮﻓﻴﺔ ﻓﻲ ﺣﻮض ﺻﻼﻟﺔ اﻟﺠﻮﻓﻲ ﺑﻬﺪف اﻻﺳﺘﻐﻼل اﻷﻣﺜﻞ ﻟﻠﻤﻮرد اﻟﻤﺎﺋﻲ واﻟﻤﺤﺎﻓﻈﺔ ﻋﻠﻴﻪ ﻣﻦ اﻻﺳﺘﻨﺰاف واﻟﻬﺪر واﻟﺘﺼﺪي ﻻﻧﺨﻔﺎض ﻣﺴﺘﻮﻳﺎت اﻟﻤﻴﺎﻩ اﻟﺠﻮﻓﻴﺔ وﺗﺪاﺧﻞ ﻣﻴﺎﻩ اﻟﺒﺤﺮ اﻟﻤﺎﻟﺤﺔ ﻓﻲ اﻟﺤﻮض . ﻳﻌﺘﺒﺮ ﻣﻜﻤﻦ ﺳﻬﻞ ﺻﻼﻟﺔ اﻟﻤﺎﺋﻲ اﻟﻤﺼﺪر اﻟﻮﺣﻴﺪ ﻟﻠﻤﻴﺎﻩ اﻟﻌﺬﺑﺔ ﻟﺘ ﻠﺒﻴﺔ اﻟﻄﻠﺐ اﻟﻤﺘﺰاﻳﺪ ﻋﻠﻰ اﻟﻤﻴﺎﻩ ﻓﻲ ﻣﺪﻳﻨﺔ ﺻﻼﻟﺔ . ﻳﺘﻢ ﺿﺦ اﻟﻤﻴﺎﻩ ﻣﻦ اﻟﺤﻮض اﻟﺠﻮﻓﻲ ﻋﺒﺮ أآﺜﺮ ﻣﻦ (1500) ﺑﺌﺮ إﻧﺘﺎﺟﻴﺔ ﺣﻴﺚ ﻳﻘﺪر ﻣﺠﻤﻮع اﻟﺴﺤﺐ اﻟﺤﺎﻟﻲ (2005م) ﻟﻠﻤﻴﺎﻩ اﻟﺠﻮﻓﻴﺔ ﻟﻼﺳﺘﺨﺪاﻣﺎت اﻟﻤﺨﺘﻠﻔﺔ ﺑﺤﻮاﻟﻲ (65) ﻣﻠﻴﻮن ﻣﺘﺮ ﻣﻜﻌﺐ وﻣﻦ اﻟﻤﺘﻮﻗﻊ أن ﻳﺰداد اﻟﺴﺤﺐ ﺳ ﻨ ﻮ ﻳ ﺎً ﺑﻤﻌﺪل ﻣﺘﻨﺎﻣﻲ ﺑﻮ اﻗﻊ 3% ﺳﻨﻮﻳﺎً ﻟﻴﺼﻞ إﻟﻰ 74 ﻣﻠﻴﻮن ﻋﺎم 2020م. وﻋﻠﻴﻪ ﻓﻤﻦ اﻟﻤﺘﻮﻗﻊ أن ﻳﺘﺮاوح اﻟﻌﺠﺰ ﻓﻲ اﻟﻤﻴﺰاﻧﻴﺔ اﻟﻤﺎﺋﻴﺔ ﻟﻠﺤﻮض اﻟﺠﻮﻓﻲ ﺑﻴﻦ 9( 9( إﻟﻰ 13 ﻣﻠﻴﻮن ﻣﺘﺮ ﻣﻜﻌﺐ ﺳﻨﻮﻳﺎً) ﺑﻴﻦ اﻟﻌﺎﻣﻴﻦ 2005 إﻟﻰ 2020م، ﺣﻴﺚ ﻳﻔﻮق اﻹﻧﺘﺎج اﻟﻜﻠﻲ ﻣﻦ اﻟﺤﻮض اﻟﺘﻐﺬﻳﺔ اﻟﻄﺒﻴﻌﻴﺔ واﻟﺼﻨﺎﻋﻴﺔ ﺑﻨﺴﺒﺔ ﺑﻴﻦ (16% إﻟﻰ 21%) أﻋﻠﻰ ﻣﻦ اﻹﻧﺘﺎج اﻵﻣﻦ ﺑﻴﻦ اﻟﻌﺎﻣﻴﻦ 2005 إﻟﻰ 2020م. اﻟﻤﻌﺪل اﻟﺤﺎﻟﻲ ﻟﻠﻀﺦ ﻏﻴﺮ ﻣﺴﺘﺪام وﺗﺪهﻮر ﺟﻮدة اﻟﻤﻴﺎﻩ اﻟﺠﻮﻓﻴﺔ واﺿﺤﺔ ﻓﻲ أﺟﺰاء آﺜﻴﺮة ﻣﻦ ﺳﻬﻞ ﺻﻼﻟﺔ . وﻗﺪ ﺗﻀﻤﻨﺖ اﻟﺪراﺳﺔ ﺑﻨﺎء ﻧﻤﻮذج رﻗﻤﻲ ﺛﻼﺛﻲ اﻷﺑﻌﺎد ﻟﺘﺪﻓﻖ وﺣﺮآﺔ اﻷﻣﻼح ﻓﻲ اﻟﻤﻴﺎﻩ اﻟﺠﻮﻓﻴﺔ ﻟﻤﺤﺎآﺎة ﻣﻜﻤﻦ ﺳﻬﻞ ﺻﻼﻟﺔ اﻟ ﺴﺎﺣﻠﻲ . ﺗﻤﺖ ﻣﻌﺎﻳﺮة اﻟﻨﻤﻮذج اﻟﺮﻗﻤﻲ وﻓﻖ اﻟﺮﺑﻂ اﻟﺰﻣﻨﻲ ﻟﻠﺤﻮض ﻓﻲ ﻣﺮﺣﻠﺔ اﻻﺳﺘﻘﺮار وﻋﺪم اﻻﺳﺘﻘﺮار ﺧﻼل اﻟﻔﺘﺮة ﻣﻦ 1992 ﻟﻐﺎﻳﺔ 2005م. ﻗﺪرت اﻟﺪراﺳﺔ اﻟﺘﻐﺬﻳﺔ اﻟﺘﺤﺖ ﺳﻄﺤﻴﺔ اﻟﺴﻨﻮﻳﺔ اﻟﻤﺘﺪﻓﻘﺔ ﻣﻦ ﺟﺒﺎل اﻟﻘﺮا ﺑـ 50 ﻣﻠﻴﻮن ﻣﺘﺮ ﻣﻜﻌﺐ /اﻟﺴﻨﺔ . ﺗﻢ إﺟﺮاء ﻣﺤﺎآﺎة ﺗﻨﺒﺆﻳﺔ ﺗﺤﺖ ﻇﺮوف ﻋﺪم اﻻﺳﺘﻘﺮار ﻟﻠﺘﻨﺒﺆ ﺑﺴﻠﻮك اﻟﻤﻜﻤﻦ ﻓﻲ اﻟﺨﻤﺴﺔ ﻋﺸﺮة ﺳﻨﺔ اﻟﻤﻘﺒﻠﺔ (ﺣﺘﻰ ﻋﺎم 2020م). ﺗﺒﻨﻰ اﻟﻤﺸﺮوع ﻣﻨﻬﺠﻴﺔ ﻹﻋﺎدة اﻟﺘﻮازن اﻟﻤﺎﺋﻲ ﻟﻠﺤﻮض إ ﻋ ﺘ ﻤ ﺎ د اً ﻋﻠﻰ ﻋﺮض ﻣﺸﻬﺪﻳﻦ أﺳﺎﺳﻴﻴﻦ، اﻷول : أﻋﺘﻤﺪ ﻋﻠﻰ ﻣﺒﺪأ اﻟﺴﻮق أ و ﻻً "business as usual" ﻣﻊ إﻋﺘﺒﺎر اﻟﺘﻐﺬﻳﺔ اﻟﺘﺤﺖ ﺳﻄﺤﻴﺔ اﻟﺴﻨﻮﻳﺔ ﺛﺎﺑﺘﺔ ﻋﻠﻰ إﻓﺘﺮ اض أن اﻟﺤﻜﻮﻣﺔ ﺳﻮف ﺗﺘﺨﺬ إﺟﺮاءات ﻟﻠﻤﺤﺎﻓﻈﺔ ﻋﻠﻰ اﻟﻨﺒﺎﺗﺎت واﻷﺷﺠﺎر اﻟﻘﺎﺋﻤﺔ ﺣ ﺎ ﻟ ﻴ ﺎً ﻓﻲ ﺟﺒﻞ اﻟﻘﺮا ﺧ ﺎ ﺻ ﺔً ﺗﻠﻚ اﻟﻮاﻗﻌﺔ ﻋﻠﻰ ﻗﻤﺔ اﻟﺠﺒﻞ ﺧﻠﻒ ﺳﻬﻞ ﺻﻼﻟﺔ، واﻟﺜﺎﻧﻲ : أﻋﺘﻤﺪ ﻋﻠﻰ ﻣﺒﺪأ اﻟﺴﻮق أ و ﻻً "business as usual" ﻣﻊ ﺗﺨﻔﻴﺾ اﻟﺘﻐﺬﻳﺔ اﻟﻤﺬآﻮرة ﺑﻮاﻗﻊ 5% ﺳﻨﻮﻳﺎً، ﻋﻠﻰ ﺧﻠﻔﻴﺔ اﻟﻨﻘﺺ اﻟﻤﺘ ﻮﻗﻊ ﻓﻲ آﻤﻴﺔ اﻟﺘﻐﺬﻳﺔ اﻷﻓﻘﻴﺔ اﻟﻤﻌﺘﻤﺪة أﺳﺎﺳﺎًً ﻋﻠﻰ ﻋﻤﻠﻴﺔ ﺗﺠﻤﻴﻊ ﻣﻴﺎﻩ اﻟﻀﺒﺎب ﻣﻦ اﻷﺷﺠﺎر ﻧ ﻈ ﺮ اً ﻟﻠﺘﺪهﻮر اﻟﻐﺎﺑﻮي اﻟﻤﺴﺘﻤﺮ ﻓﻲ ﺟﺒﺎل اﻟﻘﺮا واﻟﺬي ﻳﻤﺜﻞ اﻟﺸﺮﻳﻂ اﻟﺪاﺧﻠﻲ ﻟﻨﻄﺎق اﻟﺘﻐﺬﻳﺔ ﻟﻤﻜﻤﻦ ﺳﻬﻞ ﺻﻼﻟﺔ، ﺣﻴﺚ ﻳﺰود اﻟﺤﻮض اﻟﺴﺎﺣﻠﻲ ﺑﻤﺎ ﻧﺴﺒﺘﻪ 98% ﻣﻦ ﻣﺠﻤﻞ اﻟﺘﻐﺬﻳﺔ اﻟﻄﺒﻴﻌﻴﺔ اﻟﺴﻨﻮﻳﺔ . وﺗﻢ اﻗﺘﺮاح وﺗﻘﻴﻴﻢ ﺳﺒﻌﺔ ﻣﺸﺎهﺪ (ﺳﻴﻨﺎرﻳﻮهﺎت ) ﻟﻜﻞ ﺣﺎﻟﺔ، وذﻟﻚ ﺑﺈﺳﺘﺨﺪام اﻟﻤﺤﺎآﺎة ﻟﻔﻬﻢ واﻟﺘﻨﺒﺆ ﺑﺴﻠﻮك اﻟﻤﻜﻤﻦ ﻋﻨﺪ ﺗﻨﻔﻴﺬ ﺗﻠﻚ اﻹﺟﺮاءات ﻣﻦ ﺧﻼل ﻣﺸﺎهﺪة اﻟﺘﻐﻴﺮ ﻓﻲ ﻣﺴﺘﻮﻳﺎت اﻟﻤﻴﺎﻩ واﻷﻣﻼح ﻓﻲ اﻟﺤﻮض ﻟﻠﻔﺘﺮة 2006-2020م وهﻢ: 1) ﻧﻘﻞ ﻣﺰرﻋﺘﻲ ﺟﺮزﻳﺰ واﻟﺒﺤﻮث اﻟﺤﻴﻮاﻧﻴﺔ ﺑ ﻌ ﻴ ﺪ اً ﻋﻦ اﻟﺤﻮض اﻟﻤﺎﺋﻲ اﻟﻌﺬب، 2) ﺗﻌﻠﻴﻖ اﻟﻀﺦ ﻹﻧﺘﺎج اﻷﻋﻼف اﻟﺨﻀﺮاء ﻟﻔﺘﺮة 4 أﺷﻬﺮ ﻓﻲ اﻟﺴﻨﺔ، 3) ﺗﻐﻴﻴﺮ ﻓﻲ أﻧﻈﻤﺔ اﻟﺰراﻋﺔ واﻟﺮي ﻓﻲ اﻟﻤﺤﺎﺻﻴﻞ، 4) إﻧﺸﺎء ﻣﺤﻄﺔ ﺗﺤﻠﻴﺔ ﻣﻴﺎﻩ اﻟﺒﺤﺮ، 5) اﻟﺨﻴﺎر اﻷول واﻟﺮاﺑﻊ ﻣ ﻌ ﺎً ، 6) اﻟﺨﻴﺎر اﻷول واﻟﺜﺎﻟﺚ ﻣ ﻌ ﺎً و 7) آﻞ اﻟﺨﻴﺎرات 1( + 4+3+2 ). ﺗﺒﻴﻦ أن أي إﺟﺮاء إداري (اﻟﺨﻴﺎرات 1- 4) ﻟﻦ ﻳﺴﺘﻄﻴﻊ ﺗﺤﺴﻴﻦ اﻟﻮﺿﻊ ﺑﻤﻔﺮدة ﺧﻼل 15 ﺳﻨﺔ اﻟﻘﺎدﻣﺔ . وﺑﺎﻟﺘﺎﻟﻲ ﻳﺠﺐ دﻣﺞ اﻟﺨﻴﺎرات اﻹﺟﺮاﺋﻴﺔ ﻣﻊ ﺑﻌﻀﻬﺎ ﻟﻜﻲ ﻳﺘﻮﻗﻒ اﻟﺘﺪهﻮر وﻳﺤﺼﻞ إﺗﺰان . وﺗﺸﻴﺮ ﻧﺘﺎﺋﺞ اﻟﻤﺤﺎآﺎة إﻟﻰ أن ﻣﻨﻬﺠﻴﺔ اﻟﺨﻴﺎر اﻟﺨﺎﻣﺲ هﻲ اﻷآﺜﺮ ﻓﺎﻋﻠﻴﺔ ﺑﺎﻟﻨﺴﺒﺔ ﻟﺘﺤﺴﻴﻦ ﻣﺴﺘﻮﻳﺎت اﻟﻤﻴﺎﻩ ﺧﻼل ﻓﺘﺮة اﻟﺘﻨﺒﺆ ﺑﻴﻨﻤﺎ ﻣﻨﻬﺠﻴﺔ اﻟﺨﻴﺎر اﻟﺴﺎدس هﻲ اﻷﻓﻀﻞ ﺑﺎﻟﻨﺴﺒﺔ ﻟﺘﺤﺴﻴﻦ ﺣﺎﻟﺔ اﻟﻤﻠﻮﺣﺔ وﺗﻮﺻﻲ اﻟﺪراﺳﺔ ﺑﺘﻄﺒﻴﻖ ﻣﻨﻬﺠﻴﺔ اﻟﺨﻴﺎر اﻟﺴﺎدس ﻧ ﻈ ﺮ اً ﻷﻓﻀﻠﻴﺘﻪ ﻓﻲ اﻹدارة

v Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

اﻟﻤﺴﺘﺪاﻣﺔ ﻟﻠﺤﻮض ﻣ ﻘ ﺎ ر ﻧ ﺔً ﺑﺎﻟﺨﻴﺎر اﻟﺨﺎﻣﺲ . ﻳﺸﻴﺮ اﻻﺣﺘﻤﺎل إﻟﻰ ﺿﺮورة اﻷﺧﺬ ﻓﻲ اﻻﻋﺘﺒﺎر ﺗﻨﻔﻴﺬ إﺟﺮاءات إﺿﺎﻓﻴﺔ ﺧﻼل اﻟﻌﻘﺪﻳﻦ اﻟﻘﺎدﻣﻴﻦ ﻟﻀﻤﺎن ﺗﻠﺒﻴﺔ إﻣﺪادات ﻣﻴﺎﻩ اﻟﺸﺮب ﻟﺴﺎآﻨﻲ اﻟﻤﺪﻳﻨﺔ . ﺗﻢ دراﺳﺔ اﻟﺨﻴﺎرات اﻹدارﻳﺔ ﻋﻠﻰ ﺣﻮض ﺻﻼﻟﺔ اﻟﺠﻮﻓﻲ اﻟﺴﺎﺣﻠﻲ، واﻟﺘﻲ ﻳﻤﻜﻦ أن ﻳﺘﻢ ﺗﻄﺒﻴﻘﻬﺎ ﻓﻲ ﻣﻨﺎﻃﻖ ﺁﺧﺮى ﻟﻬﺎ ﻇﺮوف ﻣﺸﺎﺑﻬﻪ . ﺗﻢ رﺑﻂ هﺬﻩ اﻟﺪراﺳﺔ ﺑﺎﻟﻌﻤﻞ اﻟﻤﻴﺪاﻧﻲ ﻟﺘﺠﺮﺑﺔ دراﺳﺔ هﻴﺪروﻟﻮﺟﻴﺔ اﻟﺴُﺤﺐ اﻟﻤﻮﺳﻤﻴﺔ وﺗﺪهﻮر اﻷﺷ ﺠﺎر ﻓﻲ ﺟﺒﺎل ﻇﻔﺎر ودور اﻟﻤﻈﻠﺔ اﻟﺸﺠﺮﻳﺔ ﻓﻲ اﺻﻄﻴﺎد اﻟﻀﺒﺎب وذﻟﻚ ﺧﻼل ﻣﻮﺳﻢ اﻟﺨﺮﻳﻒ 2003-2005م. ﺣﻴﺚ ﺗﻢ رﺑﻂ اﻟﻌﻤﻞ اﻟﻤﻴﺪاﻧﻲ ﺑﺎﻟﺪراﺳﺔ اﻟﻨﻈﺮﻳﺔ ﻟﺘﻘﻴﻴﻢ واﺧﺘﺒﺎر ﻧﺘﻴﺠﺔ اﻟﺘﻐﺬﻳﺔ اﻟﺘﺤﺖ ﺳﻄﺤﻴﺔ ﻣﻦ ﺟﺒﻞ اﻟﻘﺮا إﻟﻰ ﻣﻜﻤﻦ ﺳﻬﻞ ﺻﻼﻟﺔ اﻟﺴﺎﺣﻠﻲ اﻟﻤﺸﺘﻘﺔ ﻣﻦ اﻟﻨﻤﻮذج اﻟﺮﻳﺎﺿﻲ اﻟﺬي ﺗﻤﺖ ﻣﻌﺎﻳﺮﺗﻪ وآﺬﻟﻚ ﻟﺘﻮﺿﻴﺢ أهﻤﻴﺔ اﺳﺘﺪاﻣﺔ اﻟﻤﻈﻠﺔ اﻟﺸﺠﺮﻳﺔ ﻓﻲ ﺟﺒﺎل اﻟﻘﺮا ﺑﺎﻟﻨﺴﺒﺔ ﻟﻤﺴﺎهﻤﺘﻬﺎ ﻓﻲ اﻟﺘﻐﺬﻳﺔ اﻟﺠﻮﻓﻴﺔ . وﺗﻘﺪر ﻧﺘﺎﺋﺞ اﻟﻨﻤﺬﺟﺔ اﻟﺮﻳﺎﺿﻴﺔ ﻟﻠﻤﻴﺎﻩ اﻟﺠﻮﻓﻴﺔ واﻟﻤﺤﺎآﺎة إﻟﻰ أن آﻤﻴﺔ ﻣﻴﺎﻩ اﻟﺘﻐﺬﻳﺔ اﻟﻄﺒﻴﻌﻴﺔ اﻟﺴﻨﻮﻳﺔ اﻟﺘﺤﺖ ﺳﻄﺤﻴﺔ اﻟﻘﺎدﻣﺔ ﻣﻦ ﺟﺒﺎل اﻟﻘﺮا ﻟﺘﻐﺬﻳﺔ ﺣﻮض ﺻﻼﻟﺔ اﻟﺠﻮﻓﻲ اﻟﺴﺎﺣﻠﻲ ﺑﺤﻮاﻟﻲ 50 ﻣﻠﻴﻮن ﻣﺘﺮ ﻣﻜﻌﺐ /اﻟﺴﻨﺔ ﻣ ﻘ ﺎ ر ﻧ ﺔً ﺑـ 53 ﻣﻠﻴﻮن ﻣﺘﺮ ﻣﻜﻌﺐ/اﻟﺴﻨﺔ اﻟﻤﺸﺘﻘﺔ ﻣﻦ اﺳﺘﺨﺮاج اﻟﻨﺘﺎﺋﺞ اﻟﻤﻴﺪاﻧﻴﺔ ﻟﻠﺘﺠﺮﺑﺔ اﻟﻤﺬآﻮرة . ﻗﺪرت اﻟﺪراﺳﺔ أن 60 إﻟﻰ 80% ﻣﻦ ﻣﺠﻤﻞ اﻟﺘﻐﺬﻳﺔ اﻟﻄﺒﻴﻌﻴﺔ اﻟﺴﻨﻮﻳﺔ ﻟﺤﻮض ﺻﻼﻟﺔ اﻟﺠﻮﻓﻲ ﺗﺄﺗﻲ ﻣﻦ ﻋﻤﻠﻴﺔ اﻟﺘﺮﺳﻴﺐ اﻷﻓﻘﻲ اﻟﺬي ﻳﺤﺪث ﻧﺘﻴﺠﺔ ﺗﺠﻤﻴﻊ اﻷﺷﺠﺎ ر ﻟﻤﻴﺎﻩ اﻟﻀﺒﺎب أﺛﻨﺎء ﻓﺼﻞ اﻟﺨﺮﻳﻒ . ﺗﺜﺒﺖ اﻟﺘﺠﺮﺑﺔ اﻟﻌﻤﻠﻴﺔ ﻟﺪراﺳﺔ اﺻﻄﻴﺎد اﻟﻀﺒﺎب ﻓﻲ ﺟﺒﺎل ﻇﻔﺎر ﺑﻤﺎ ﻻ ﻳﺪع ﻣ ﺠ ﺎ ﻻً ﻟﻠﺸﻚ إﻟﻰ أهﻤﻴﺔ اﻟﻨﺒﺎﺗﺎت ﻓﻲ ﺟﺒﻞ اﻟﻘﺮا آﻤﺼﺪر رﺋﻴﺴﻲ ﻟﻠﺘﻐﺬﻳﺔ اﻟﺠﻮﻓﻴﺔ اﻟﺴﻨﻮﻳﺔ ﻟﻠﻤﻜﻤﻦ اﻟﺴﺎﺣﻠﻲ ﻣﻦ ﺧﻼل اﻟﻤﺴﺎهﻤﺔ ﻓﻲ اﻟﺘﺴﺎﻗﻂ اﻷﻓﻘﻲ . وﻳﺸﻬﺪ اﻟﺠﺒﻞ ا ﻧ ﺨ ﻔ ﺎ ﺿ ﺎً ﺳ ﺮ ﻳ ﻌ ﺎً ﻓﻲ اﻣﺘﺪاد اﻟﻐﻄﺎء اﻟﻨﺒﺎﺗﻲ، وهﻜﺬا ﻓﺈن آﻤﻴﺎت اﻟﻤﻴﺎﻩ اﻹﺿﺎﻓﻴﺔ اﻟﻤﺘﻮاﻓﺮة ﻓﻲ اﻟﻤﺮاﻋﻲ ﻣﻦ ﺧﻼل اﺟﺘﺬاب اﻷﺷﺠﺎر ﻟﻠﻤﻴﺎﻩ اﻟﻀﺒﺎﺑﻴﺔ أﺧﺬت ﻓﻲ اﻟﺘﻨﺎﻗﺺ، ﻣﻤﺎ ﻳﻌﻨﻲ اﻧﺨﻔﺎض آﻤﻴﺔ اﻟﻤﻴﺎﻩ اﻟﻤﺘﻮاﻓﺮة ﻣﻦ هﺬا اﻟﻤﺼﺪر ﻟﺘﻐﺬﻳﺔ ﻣﺴﺘﻮدﻋﺎت اﻟﻤﻴﺎﻩ اﻟﺠﻮﻓﻴﺔ ﻓﻲ اﻟﺠﺒﻞ وﻓﻲ ﺣﻮض ﺳﻬﻞ ﺻﻼﻟﺔ اﻟﺴﺎﺣﻠﻲ . ﺗﻢ اﺗﺨﺎذ إﺟﺮاءات ﻣﻦ ﻗﺒﻞ اﻟﺤﻜﻮﻣﺔ ﻟﺘﺤﻔﻴﺰ اﺳﺘﺪاﻣﺔ اﻟﻤﻈﻠﺔ اﻟﺸﺠﺮﻳﺔ ﻓﻲ اﻟﺠﺒﻞ ﻣﻦ ﺧﻼل ﺗﺨﻔﻴﺾ إﻋﺪاد اﻹﺑﻞ ﻓﻲ ﻣﺤﺎﻓﻈﺔ ﻇﻔﺎر اﻟﺘﻲ ﻣﻦ ﺧﻼل اﻟﺮﻋﻲ ﺗﻬﺪد اﻟﻐﺎﺑﺎت و ﺧ ﺎ ﺻ ﺔً ﺗﻠﻚ اﻟﻮاﻗﻌﺔ ﻋﻠﻰ ﻗﻤﺔ اﻟﺠﺒﻞ ﺧﻠﻒ ﺳﻬﻞ ﺻﻼﻟﺔ اﻟﺘﻲ ﺗﺴﺎهﻢ ﻓﻲ ﺗﺮﺳﻴﺐ ﻣﻴﺎﻩ اﻟﻀﺒﺎب وﺑﺎﻟﺘﺎﻟﻲ ﻓﻲ ﺗﻐﺬﻳﺔ اﻟﻤﺴﺘﻮدع اﻟﻤﺎﺋﻲ اﻟﺴﺎﺣﻠﻲ ﺑﺼﻼﻟﺔ . وﻗﺎﻣﺖ وزارة اﻟﺒﻠﺪﻳﺎت اﻹﻗﻠﻴﻤﻴﺔ واﻟﺒﻴﺌﺔ وﻣﻮارد اﻟﻤﻴﺎﻩ ﺑﺈﻧﺸﺎء ﻣﺸﺘﻞ ﻧﺒﺎﺗﻲ ﻓﻲ ﺟﺒﻞ اﻟﻘﺮا (ﻣﻨﻄﻘﺔ ﻗﻴﺮون ﺣﻴﺮﺗﻲ - 872 ﻣﺘﺮ ﻓﻮق ﺳﻄﺢ اﻟﺒﺤﺮ ) ﺑﻤﺤﺎﻓﻈﺔ ﻇﻔﺎر ﻓﻲ ﻋﺎم 2005م وﺳﻴﺘﻢ ﺗﻨﻔﻴﺬ ﺧﻄﻂ وﺑﺮاﻣﺞ هﺎدﻓﺔ ﻻﺳﺘﺰراع أﻧﻮاع ﻣﺨﺘﻠﻔﺔ ﻣﻦ اﻟﻨﺒﺎﺗﺎت ﺑﻐﺮض إآﺜﺎرهﺎ وﻧﺸﺮهﺎ ﻋﻠﻰ ﻧﻄﺎق أوﺳﻊ ﻟﺘﻌﺰﻳﺰ ﺣﻤﺎﻳﺔ اﻷﺷﺠﺎر اﻟﻤﺤﻠﻴﺔ وإﻋﺎدة اﻟﻐﻄﺎء اﻟﻐﺎﺑﻮي ﻻ ﺳﻴﻤﺎ وأن ﻣﺤﺎﻓﻈﺔ ﻇﻔﺎر ﺗﺤﺘﻔﻆ ﺑﺄآﺜﺮ ﻣﻦ 750 ﻧﻮع ﻧﺒﺎﺗﻲ، ﻣﻨﻬﻢ 50 ﻧﻮع ﻣﺴﺘﻮﻃﻦ ﻓﻲ اﻷﻗﻠﻴﻢ . هﺬﻩ اﻟﺪراﺳﺔ ﺗﺆآﺪ أهﻤﻴﺔ إﺟﺮاء ﺑﺮﻧﺎﻣﺞ ﻃﻮﻳﻞ اﻟﻤﺪى ﻟﺰراﻋﺔ اﻷﺷﺠﺎر ﺑﺎﻟﺠﺒﻞ ﻹﻋﺎدة اﻟﺘﺄهﻴﻞ اﻟﻐﺎﺑﻮي وﺗﻐﺬﻳﺔ اﻟﺨﺰان اﻟﺠ ﻮﻓﻲ ﻟﻤﻴﺎﻩ ﺻﻼﻟﺔ . وﺗﺆآﺪ اﻟﺪراﺳﺔ اﻻﻗﺘﺮاح ﺑﺘﻨﻔﻴﺬ ﻋﻤﻠﻴﺎت اﺳﺘﺰراع اﻷﺷﺠﺎر اﻟﻤﺤﻠﻴﺔ ﻓﻲ ﻣﻨﺎﻃﻖ اﻟﺤﺸﺎﺋﺶ ﻟﺘﻌﺰﻳﺰ اﺳﺘﺪاﻣﺔ اﻟﻐﻄﺎء اﻟﺸﺠﺮي ﻓﻲ ﺟﺒﺎل ﻇﻔﺎر ﺑﻐﺮض ﺗﺤﻔﻴﺰ ﻋﻤﻠﻴﺔ ﺗﺠﻤﻴﻊ ﻣﻴﺎﻩ اﻟﻀﺒﺎب ﻣﻦ ﺧﻼل ازدﻳﺎد اﻋﺘﺮاض اﻷﺷﺠﺎر ﻟﻠﻀﺒﺎب وﺑﺎﻟﺘﺎﻟﻲ زﻳﺎدة ﻓﻲ إﻧﺘﺎﺟﻴﺔ اﻟﺤﺸﺎﺋﺶ اﻟﻄﺒﻴﻌﻴﺔ ﻓﻲ ا ﻟﺠﺒﻞ واﻟﺘﻐﺬﻳﺔ اﻟﺠﻮﻓﻴﺔ اﻟﺴﻨﻮﻳﺔ ﻟﻤﻜﻤﻦ ﺻﻼﻟﺔ اﻟﺴﺎﺣﻠﻲ . وﻓﻴﻤﺎ ﻳﺘﻌﻠﻖ ﺑﻤﺒﺪأ اﻟﺘﻐﺬﻳﺔ اﻟﺼﻨﺎﻋﻴﺔ ﺑﺎﻟﻤﻴﺎﻩ اﻟﻤﻌﺎﻟﺠﺔ ﻓﻲ اﻟﺸﺮﻳﻂ اﻟﺴﺎﺣﻠﻲ ﻟﺤﻮض ﺻﻼﻟﺔ ﻟﻜﺒﺢ ﺗﺪاﺧﻞ ﻣﻴﺎﻩ اﻟﺒﺤﺮ ﻓﻘﺪ ﺗﻢ ﻃﺮﺣﻪ ﻣﻦ ﻗﺒﻞ اﻟﺒﺎﺣﺚ ﻓﻲ 1998م. ﺗﻢ وﺿﻊ ﻋﻤﻠﻴﺔ ﺗﺠﻤﻴﻊ وﻣﻌﺎﻟﺠﺔ ﻣﻴﺎﻩ اﻟﺼﺮف اﻟﺼﺤﻲ ﻟﻤﺪﻳﻨﺔ ﺻﻼﻟﺔ وﻣﻨﺬ اﻟﻌﺎ م 2003م ﺑﺪأت ﻋﻤﻠﻴﺔ اﻟﺤﻘﻦ اﻟﺠﻮﻓﻲ اﻟﻤﺒﺎﺷﺮ ﻟﻠﻤﻴﺎﻩ اﻟﻤﻌﺎﻟﺠﺔ ﻓﻲ ﺁﺑﺎر ﺟﻮﻓﻴﺔ ﺑﻐﺮض ﻋﻤﻞ ﺣﺎﺟﺰ هﻴﺪروﺳﺘﺎﺗﻴﻜﻲ ﻟﻤﻨﻊ ﻋﻤﻠﻴﺔ ﺗﺪاﺧﻞ ﻣﻴﺎﻩ اﻟﺒﺤﺮ ﻓﻲ اﻟﺤﻮض اﻟﺴﺎﺣﻠﻲ . ﻓﻲ هﺬﻩ اﻟﺪراﺳﺔ ﺗﻢ اﺧﺘﺒﺎر ﺗﺄﺛﻴﺮ اﻟﺠﻮاﻧﺐ اﻟﺘﻄﺒﻴﻘﻴﺔ ﻟﻠﻤﺨﻄﻂ اﻟﻤﺘﻌﻠﻖ ﺑﺎﻟﺘﺮﺷﻴﺢ اﻟﺼﻨﺎﻋﻲ ﻟﻠﻤﻴﺎﻩ اﻟﻤﻌﺎﻟﺠﺔ ﻟﻜﺒﺢ ﺗﺪاﺧﻞ ﻣﻴﺎﻩ اﻟﺒﺤﺮ وذﻟﻚ ﺑﺎﺳﺘﺨﺪام اﻟﻨﻤﺬﺟﺔ اﻟﺮﻳﺎﺿﻴﺔ ﻟﺘﺪﻓﻖ اﻟﻤﻴﺎﻩ وﺣﺮآﺔ اﻷﻣﻼح ﻓﻲ اﻟﻤﻴﺎﻩ اﻟﺠﻮﻓﻴﺔ . ﺗﻢ ﻣﻘﺎرﻧﺔ اﻟﺒﻴﺎﻧﺎت اﻟﻤﺸﺘﻘﺔ ﻣﻦ اﻟﻨﻤﻮذج اﻟﺮﻳﺎﺿﻲ ﺑﺒﻴﺎﻧﺎت اﻟﻤﺮاﻗﺒﺔ اﻟﻤﻴﺪاﻧﻴﺔ ﻟﻤﺸﺮوع اﻟﺘﻐﺬﻳﺔ اﻟﺼﻨﺎﻋﻴﺔ . ﺑﻴﻨﺖ ﻧﺘﺎﺋﺞ اﻟﻨﻤﺬﺟﺔ اﻻﺣﺘﻤﺎﻟﻴﺔ ﻟﺘﺪﻓﻖ وﺣﺮآﺔ اﻷﻣﻼح ﻓﻲ اﻟﻤﻴﺎﻩ اﻟﺠﻮﻓﻴﺔ ﺑﺄن ﻋﻤﻠ ﻴﺔ ﺣﻘﻦ اﻟﻤﻴﺎﻩ اﻟﻤﻌﺎﻟﺠﺔ ﻓﻲ اﻟﺸﺮﻳﻂ اﻟﺴﺎﺣﻠﻲ ﺗﺴﺎﻋﺪ ﻓﻲ ارﺗﻔﺎع ﻣﺴﺘﻮﻳﺎت اﻟﻤﻴﺎﻩ اﻟﺠﻮﻓﻴﺔ ﻓﻲ اﻟﻤﻨﺎﻃﻖ اﻟﻤﺠﺎورة ﻵﺑﺎر ﺧﻂ اﻟﺘﻐﺬﻳﺔ وﻣﻦ اﻟﻤﺘﻮﻗﻊ أن ﺗﻌﻤﻞ ﻋﻠﻰ دﻓﻊ ﻧﻄﺎق اﻟﻤﻠﻮﺣﺔ ﻟﻠﺨﻠﻒ ﺑﻮاﻗﻊ 700 ﻣﺘﺮ ﻓﻲ ﻋﺎم 2019م . .

vi Mahaad Shammas TRITA LWR PhD Thesis 1031

ACKNOWLEDGMENTS

IN THE NAME OF THE ALMIGHTY ALLAH

I would like to express my sincere gratitude and appreciation to His Majesty Sultan Qaboos bin Said, Sultan of Oman, may Allah protect him and to the Minister of the MRMEWR & his undersecretaries and the relevant Omani Authority for giving me the opportunity to pursue higher studies. I also wish to thank all those people who have made this project possible. I would like to acknowledge many people, my family, friends and colleagues for help and support. First of all, I wish to express my deepest gratitude to my su- pervisors Prof. Gunnar Jacks and Prof. Roger Thunvik at the Dept. of Land and Water Resources Engineering (LWR) at the Royal Institute of Technology (KTH), Stockholm as well as Prof. Waleed Al-Zubari vice-Dean of Technological Studies, College of Graduate Studies, Arabian Gulf University, Bahrain (the external advisor). In addition to providing their constructive comments, scientific guidance, valuable comments on my thesis, they have provided helpful advice throughout the work on the thesis and in showing me how to look for the essence of things. Their critical review of the thesis greatly improved its clarity. This research was supported by a grant from the owner of Quality and Innovation Establishment Enterprises in the Sultanate of Oman. I also wish to extend special thanks and appreciation to my elder brother Ali, the owner. In addition to providing continuous financial support, he has provided encouragement, motivation and advice along the way. I wish to extend my sincere gratefulness and appreciation to the MRMEWR staff, especially the staff of the GIS & remote sensing, especially in the planning department, as well as to the staff of the DGEWRDG, especially to the staff of the monitoring and studies section in DWR for support, encouragement and providing me with valued data and information. It is a pleasure to thank the following for their assistance in various ways: Mansoor Mahwi Amer- jeed, Abdullah Mohammad Baawain, Ali Abdullah Al-Makhzoom, Hussain Abdullah Al-Yafai and Salim Ahmed Sakroon. I also thank everybody at the dept. of LWR for creating a nice and friendly atmosphere in the everyday life. I wish to record my appreciation to Prof. Emeritus Klas Cederwall, Prof. Per-Erik Jansson, Bo Olofsson, Jon Petter Gustafsson, Prosun Bhattacharya, Prof. Bengt Hultman and Haile Estifanos, for sharing their knowledge and support. Furthermore, I wish to express my gratitude towards Aira Saarelainen, Ann-Catrine Norrström, Christina Ek, Ann Fylkner, Lars-Erik Svahn, Jerzy Buczak, Britt Chow, Joanne Fernlund and Kerstin Indebetou for assistance with all kinds of practical matters. Thanks also to Olle Wahlberg, Arifuzzaman Mohammed, Ahmed Faruque Ferdous, Aziz Hasan, Dorothy Ferberg, Jennifer McConville, Armin Hajivand and Samuel Azasu for the useful discussions, encouragement, support and friendship. Thanks are also due to Paul Sharples of MRMEWR, Oman and Paul Wilkinson for the language correc- tion. I am most grateful to my brothers, Said, Ali and Salim, family and friends in Oman for their support and encouragement throughout all these years while doing this project. Many thanks are due to the family of my wife for their hospitality to my daughter, Areej, in 2005 and care of my children. I am most grateful to the wife of my elder brother Safa, and to my wife’s sisters for care and helping with my children. Last but not least, special thanks to my beloved wife Muna, who took care of our children during the course of my studies and to my children, who bore with me the difficult times of the project period and for understanding my frequent absences.

vii Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

viii Mahaad Shammas TRITA LWR PhD Thesis 1031

TABLE OF CONTENTS Acknowledgments...... vii Table of contents...... ix Acronyms and Abbreviations...... xi ABSTRACT ...... 1 Introduction...... 1 Aims and objectives...... 2 Previous studies...... 2 Problem identification ...... 2 Study approach...... 3 Outline of the study...... 3 Description of the study area...... 3 Evaporation on the plain...... 4 Hydrogeology...... 5 Groundwater development and management ...... 5 Natural recharge...... 6 Vertical precipitation...... 6 Horizontal precipitation...... 6 Discharge from the groundwater ...... 6 Groundwater management ...... 6 Monitoring of aquifer performance ...... 7 Recharge/flood protection dams ...... 7 The direct injection of reclaimed wastewater...... 7 Reduction of the camel population ...... 7 Available measures to government...... 8 Jabal reforestation...... 9 Irrigation water distribution and efficiency of water use ...... 9 Seawater Desalination Plant ...... 11 Materials and Methods ...... 11 Numerical modelling development ...... 11 Fogwater Collection experiment ...... 12 Results and discussion...... 12 Introduction...... 12 Piezometric surface ...... 14 Solute transport...... 15 Mass balance analysis...... 15 Model limitations...... 16 Conclusion and Recommendations ...... 16 Flow model- Conclusions...... 16 Solute transport model– Conclusions ...... 18 Recommendations...... 18 References...... 19

ix Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

x Mahaad Shammas TRITA LWR PhD Thesis 1031

ACRONYMS AND ABBREVIATIONS Al-Rub Al-Khali the Empty Quarter Ain Spring cm centimetre DCFC Dhofar Cattle Feed Company owns Garziz and Sahalnawt farms D&M I; CDM Dames and Moore International; Camp Dresser and McKee, Inc DGEWRDG Directorate General of Environment and Water Resources in Dhofar Gover- norate, MRMEWR DWR Department of Water Resources Affairs in the DGEWRDG EC Electrical Conductivity FAO Food and Agriculture Organisation of the United Nations GDP Gross Domestic Product GIS Global Information System ha Hectares HMR Hussam Mohammed Al Rawahi Jabal Mountain km kilometres Khareef Monsoon l/s litres per second m amsl metres above mean sea level mg/l milligrams per litre mm/d millimetres per day Mm3 Million Cubic Metres μS/cm micro Siemens/cm, a measure of electrical conductivity (EC) MAF Ministry of Agriculture and Fisheries of the Sultanate of Oman MCM Million Cubic Metres MRMEWR Ministry of Regional Municipalities, Environment and Water Resources of the Sultanate of Oman MWR (former) Ministry of Water Resources of the Sultanate of Oman NWD Net Water Demand NWI National Wells Inventory OR Omani Rial, currently one OR equivalent to 2.58 US Dollars PCDESR (former) Planning Committee for Development and Environment of the Southern Region, Sultanate of Oman PD-GIS The Planning Department-Geographic Information System section for MRMEWR SSDSCo Salalah Sanitary Drainage Services Company STP Sewage Treatment Plant TDS Total Dissolved Solids Wadi Valley yr Year

xi Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

xii Mahaad Shammas TRITA LWR PhD Thesis 1031

ABSTRACT A numerical flow model was developed for the Salalah coastal aquifer using both the MODFLOW computer code and the MT3DMS computer code to assist in the analysis of freshwater flow and saltwater intrusion. The underflow was derived from the developed numerical groundwater flow modelling and calibration on hydraulic heads of 1992. A model-calculated water budget indicates that 51 million cubic metres per year of freshwater recharge the Salalah plain aquifer system, of which 98% of this water is underflow originating from Jabal AlQara, and the remaining 2% is the recharge on the plain. Two baseline scenario simulations were run to calculate the potentiometric surface and salinity distribution for the "business as usual" conditions (no-management interference) of the aquifer for the period 2006 until 2020. Baseline scenario A, assumes "business as usual" and the underflow (constant recharge) to continue the same and baseline scenario B, supposes "business as usual" and the underflow to decrease (changing recharge) at 5% annually. The effectiveness of seven scenarios under each baseline scenario proposed in this work was assessed in comparison with the "business as usual" conditions. The developed simulation model was used to predict the distribution of the potentiometric surface, salinity distribution, and mass balance under these proposed scenarios for the prediction period 2006-2020. The experimental work in Jabal AlQara was linked with the theoretical study of the flow model to optimize the recharge analytically in order to evaluate the output of the recharge that was obtained by the calibrated flow model. The investigation of fogwater collection demonstrates the importance of the vegetation in Jabal AlQara as a source of subsurface recharge by contributing to the horizontal precipitation. This project estimated that the horizontal precipitation caused by fogwater capture by the Jabal vegetation, contributes to the annual natural recharge by 60% to 80%. The experimental studies on fogwater harvesting in Dhofar demonstrated the importance of vegetation in Jabal AlQara as the main source of the annual underflow to the Salalah coastal aquifer. The extent of tree cover over parts of the Jabal is rapidly declining; in turn water from fogwater collection may decrease. This means that there will be a decrease in the quantities of available water from this source to recharge the aquifers in the Jabal and the Salalah aquifer. Measures have been taken by the government to enhance the sustainability of the Jabal vegetation through the reduction of the camel population, which, by browsing, threatens the fogwater collecting forest on the mountain crest behind the Salalah plain. In addition, the government (MRMEWR) established a plant nursery in Jabal AlQara (Qai- roon hairriti- about 872 m amsl) to enhance the conservation as a result of transplantation of the indigenous plant species to combat desertification and restore the plant canopy. The ecosystem of the Dhofar region supports more than 750 terrestrial plant species, out of which about 50 are endemic. This study stresses the importance of implementing a major programme to enhance fogwater collection. Tree planting in the Jabal grassland is proposed for reforestation with the principle purpose of causing an increase in fogwater interception to benefit grassland production and increase the recharge of the Salalah groundwater aquifer. This study investigated the effectiveness of the artificial infiltration, through the application of reclaimed treated sewage recharge, to halt the salinity of the Salalah aquifer using a modelling technique. The study argues that the injection scheme is effective in pushing back the saline zone front by 700 metres in 2019.

Ocean (Ghassemi, et al., 1996), Bahrain (Zubari et al., INTRODUCTION 1997, Zubari 1999, Al-Shabaani, A. H 1999, Zubari 2005 and Zubari & Lori 2005), United Arab Emirates Most of the coastal areas around the globe depend aquifers (Rizk et al., 1997), Lebanon (Sadek & El totally on coastal aquifers as the major source of wa- Fadel 1998), the Gaza Strip in Palestine (Yakirevich et ter. There are many sources of groundwater con- al., 1998, Hamdan, 1999 and Al-Yaqubi & Al-Jamal tamination as a result of human influence such as 2002), the Nile Delta aquifer in Egypt (Amer, 1995, seawater intrusion (Goudie, 1993). This problem is Sherif & Amer 1995, Sherif, 1999 and Sherif & Singh more severe in arid and semi-arid regions where the 2002), Cyprus and Rhodes (Greece) (Prieto, 2001), groundwater constitutes the main freshwater re- Coastal Alluvial Aquifer of Northern Oman-Eastern source, as with the case of the Salalah plain aquifer. Batinah coastal plain- (Weyhenmeyer & Waber 3% of seawater mixed with the freshwater in a 2002), Kuwait (Al-Murad, 1994 and Al-Rashed & Al- coastal aquifer would render the freshwater resource Senafy 2000) and the north-eastern coast of Australia unsuitable for human consumption (Sherif & Singh (Zhang, et al., 2004). 2002). The Salalah plain is underlain by a shallow limestone Seawater intrusion has been detected in many coastal aquifer, which extends north up to the foot of Jabal aquifer areas all over the world, as in the Quaternary AlQara, and south to the Hafah coast (Fig. 1). Qua- aquifer West of Tripoli, Libya (Belaid & El-Fateh ternary deposits that include Wadi alluvium, a Cal- 1995), Tripoli, Libya (Sadeg, 1996), the coastal aqui- carenite layer, underlain by limestone layers, consti- fer in South and South East Asia (Jacks & Ra- tute the Salalah aquifer. The coastal plain aquifer is jagopalan 1996), Nauru Island in the central Pacific

1 Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

a b

Fig. 1 The site location of the study area. Map of Sultanate of Oman (a), photograph of Salalah plain and Jabal Al- Qara (b(, and satellite image of Salalah plain and adjacent Jabal Al-Qara (c). historically the only natural source of water supply in 4. To study the relationship between the horizontal the Salalah plain. Currently (2005) the average pump- precipitation in Jabal AlQara and groundwater ing rate is more than the recharge rate. Seawater in- recharge, and the groundwater modelling of the trusion has been reported in the Salalah plain aquifer plain aquifer (Paper 3). by the author (1998 & 2002), and Geo-Resources 5. To design the aquifer sustainable management (2004). This project uses MODFLOW, a three- options with which future management proc- dimensional simulation flow model, steady state and esses for the Salalah coastal freshwater aquifer transient in saturated zone flow, and MT3DMS for can be evaluated and assessed for proper man- solute transport. The model is used to develop the agement using the established model (Paper 4). aquifer domain and predict the water level variations 6. To study the effectiveness of reusing the treated and salinity changes in the Salalah coastal aquifer and wastewater on halting salinity intrusion into the design the sustainable management of the aquifer. Salalah plain aquifer (Paper 5). Aims and objectives Previous studies The aim of the study was to determine a number of The water resources of the Salalah plain and Jabal options that could be implemented in the region to AlQara have been studied by a number of Consult- provide water services to the growing population as ants, Ministries and Researchers since the mid-1970s. well as to reduce the saltwater intrusion on the (PAWR, 1986; WS Atkins, 1989 & 1990; Moot groundwater resource currently being impacted by MacDonald, 1996; COWIconsult, 1990 & 1992; over-abstraction. This project proposed sustainable FAO, 1992; D&MI, 1991, 1992, 1993 & 1997; De management options for the plain aquifer and the Jong et al., 1995; O’Boy, 1995; Milligan & Gharbi, scenarios were examined using numerical modelling. 1995; Chebaane & Alesh, 1995; Al-Mashaikhi, 1997; Each scenario predicted the aquifer hydraulic heads ENTEC, 1998; Shammas, 1998 & 2002; the National and salinity intrusion in the coming 15 years. Water Resources Master Plan by Binnie, 1999; Elhag The main objectives of this study are as follows: & Ghawas 2000; Baawain & Abu-Ashour 2002; 1. To determine the groundwater quality condi- Alesh, 1998 & 2003; Al-Hakmani, 2003; Qatan, 2003; tions by investigating seawater intrusion (Paper Geo-Resources, 2004; HMR, 2004; Renardet, 2004; 1). Hildebrandt et al., 2004; Hildebrandt 2005; and 2. To provide a rational quantitative understanding Hildebrandt & Eltahir 2006. of the hydrogeologic system of the Salalah plain and establish the expected exhaustion of the aq- Problem identification uifer with respect to the time (Paper 2). One of the main challenges in coastal aquifers is to 3. To use the established MODFLOW & provide the short-term water demand through ab- MT3DMS numerical codes for the study and straction from the coastal aquifers while maintaining simulate the hydrodynamics of the aquifer (Pa- long-term aquifer water balance. Increased extraction per 1). of groundwater and reduction of flow towards the

2 Mahaad Shammas TRITA LWR PhD Thesis 1031

coast has caused the saltwater interface to move the 30th January 2007. DOI:10.1007/s00254- inland (Paper 1). This could further proceed due to 007-0673-2 the unbalanced situation in the aquifer water budget II. Shammas M. I. and Jacks G, 2006. Management (Paper 2). of the Salalah aquifer, Oman. Submitted to Consequently, seawater intrusion is expected to con- Hydrogeology Journal in the 20th June 2006. tinue to increase, which will cause serious problems III. Shammas M. I., 2007. Impact of the Al-Qara if solutions, such as the resource management op- mountain fogwater forest on groundwater re- tions being proposed in this study, are not imple- charge in the Salalah coastal aquifer, Sultanate of mented. To help with this problem, a pond injection Oman. The International Journal of Ecohydrol- system was already proposed in 1998 (Shammas, ogy & Hydrobiology, Vol. 7, No 1, 37-49, 2007. 1998), but in view of the permeable aquifer condi- IV. Shammas M. I and Thunvik R, 2007. Predictive tions, well injection was chosen and the injection simulation of flow and solute transport for man- scheme started in April 2003. However, the 9.4 Mm3 agement of the Salalah coastal aquifer, Oman. being injected till the end of 2005 is not sufficient to Submitted to Water Resources Management balance the water budget of the aquifer (Papers 1& Journal in the 6th April 2007. 2). V. Shammas M. I, 2007. The effectiveness of artifi- Study approach cial recharge in combating seawater intrusion in the Salalah coastal aquifer, Oman. Accepted for The main approaches of this study are: - how to publication in Environmental Geology Journal bring balance between aquifer recharge and abstrac- in the 20th January 2007. tion? What are the available alternatives and the effectiveness of each in introducing an effective solu- Articles published or in press are reproduced by tion to the problem? What is the best groundwater permission of the respective journals. management methodology to be used to combat the Salalah aquifer salinisation? DESCRIPTION OF THE STUDY AREA Modelling has been done to investigate the plain aq- Salalah is a city located 1,100 km from Muscat the uifer hydrogeological flow system (Paper 1 & 2) and capital. Salalah is the second largest city in the Sul- to understand the effectiveness of the artificial infil- tanate of Oman with a population of 134,000 and a tration scheme (Paper 5). In addition, the actual con- growth rate of about 2.2% a year (Oman Census dition of the aquifer system and prediction of the 2003). Public administration accounts for 27% of the groundwater situation due to present/future abstrac- total employment in Salalah (Oman census 1993 tion can be simulated by modelling, which can then data). This is followed by construction (16%), trading subsequently be used for the evaluation/ suggestion (16%), manufacturing (9%) and agriculture (4%). It of management scenarios to halt saline intrusion (Pa- was found that 18% of the area is being used for ag- per 4). riculture out of the total developed area in Salalah. The study was linked instrumentally with the field Agricultural net benefits contribute marginally to the experiments on investigating the hydrology of a de- national economy (<3% GDP) (Al sulaimani, 2003). grading semi-arid seasonal cloud forest in Dhofar, The ecotourism industry is growing steadily in Dho- which are intended to evaluate the output of the re- far as the region is distinguish by a unique climate charge that was optimized by the calibrated flow found nowhere else in the Arabian Peninsula. Ecot- model. These field experiments were also designed to ourism during the southern monsoon season demonstrate the sustainability of the Jabal AlQara “Khareef” is increasing. The number of tourists has woodlands in terms of the aquifer recharge, as it acts increased by about 26% between 2003 (167,000) and as the surface Salalah aquifer catchment and provides 2004 (about 210,000) and by more than 14% be- the plain aquifer with 98% of its annual natural re- tween 2004 and 2005 (240,000). The census was charge (Paper 3). taken in the monsoon period between 21/06 and 21/09 each year. This will increase the domestic wa- Outline of the study ter demand in Salalah and the wastewater effluents. This thesis is based on the following papers, which Salalah Sanitary Drainage Services Co. (SSDSCo) re- will be referred to by their roman numbers: ported that the wastewater influent flow has in- 3 I. Shammas M. I. and Jacks G, 2002. Seawater increased from 19,618 m as a daily average in June to 3 3 trusion in the Salalah coastal aquifer, Oman. 20,785 m in July and to 28,000 m in the first week Proceedings of the International conference on of August 2006. water resources management in arid regions, Figure (2a) shows the traffic on the road to Ain Gar- (Warmar), 2002 March 23-27, Kuwait. Sherif, ziz (110 m amsl), which is about 10 km from the cen- M., Singh V.P., Al-Rashed M. (editors). A.A. tre of Salalah. Figure (2b) shows the underflow in Balkema, Netherlands, Swets& Zeitlinger, Lisse, Ain Tubrak. Ain Tubrak (70 m amsl) is a perennial ISBN 90 5809 3654, Vol. 3. 323-333. Revised type of spring, situated at the Jabal front outside the and resubmitted to Environmental Geology plain aquifer sub-basin in the east of Salalah, about 7 Journal in the 26th October 2006. Published in km from the coast, which yields about 1 Mm3/yr

3 Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

a b

Fig. 2 The typical ecosystem in Jabal Al-Qara front (a) the road to Ain Garziz, and (b) Ain Tubrak (Sep. 2006) from Umm Er Radhumma Formation. The springs Concerning the evaporation issue and its importance in Salalah are also a tourist’s destination. Dhofar in the irrigation scheme on the Salalah plain, the au- governorate has about 360 water springs, some of thor has executed a field survey, especially in the which are perennial (flow constant), which include farms that irrigate grass crops. The survey concerns Ain Sahalnawt, Razat, Tubrak etc. The water quality the timings of irrigation periods in the farms. The found at Jabal front Ains (springs) is currently within survey took place between the 19th and 30th August 500 mg/l TDS, and there is an apparent strong link 2005. The author asked the farmers some questions between Khareef rainfall and spring flow. such as: how many times per day do the farmers irri- The industrial and commercial sectors in Salalah are gate their farms? How many cuttings do the farmers also growing. The issuance of new laws and regula- make of the grass? tions is encouraging local and international compa- Farmers irrigate grass crops on the Salalah plain as nies to start work in Salalah, and this includes Royal follows: Decree No. 62/2006 (that was issued in 20 June • During the hot months (i.e. March, April, May 2006) concerning the law on the establishment of a and June), the farmers irrigate the grass for two Salalah free zone. Therefore, the water demand for to four hours between 16:00 and 20:00 hours the industrial sector will also increase. and the next day not operational day. Evaporation on the plain • During the Khareef season months (i.e. July and August), the farmers irrigate the grass for two to Regular monitoring of evaporation using the Piche four hours between 16:00 and 20:00 hours and method is carried out at only one site on the Salalah then they will not irrigate the crops at all for the plain- the Salalah airport at an elevation of 20 m next four to five days. amsl. The maximum average monthly evaporation values occur during January, December, February • During the months of November, December and November with a rate of 11.33, 11.15, 9.35 and and January, Salalah receives the northerly wind 9.13 mm/day, respectively. The lowest rates occur and sometimes the wind will be strong, espe- during the Khareef when extensive cloud cover sig- cially during December and January, so the nificantly restricts the evaporative potential, and an farmers irrigate the grass for two to four hours average value of 2.23 and 1.75 mm/day occurs dur- between 16:00 and 20:00 hours every two to ing July and August, respectively. The hot months three days. (i.e. March, April, May and June), have average Farmers irrigate vegetables on the Salalah plain as evaporation values of 8, 7.12, 5.85 and 5 mm/day, follows: respectively. • During the hot months (i.e. March, April, May Maximum evaporation occurs during December, and June), vegetable irrigation lasts for five to six January (>10 mm/day) and November, February (>9 hours between 15:00 and 20:00 hours and then mm/day), with the lowest evaporation rates during there will be no irrigation for the next two to the monsoon, typically between 2 and 4 mm/day three days. (Renardet, 2004). The maximum mean evaporation of about 11 mm/day is during January when the • During the Khareef season months (i.e. July and most intense north winds occur and the lowest August), the farmers irrigate the vegetables for evaporation mean is about 2 mm/day, during the five to six hours between 15:00 and 20:00 hours cloud covered humid monsoon (O’Boy, 1995). and then there will be no irrigation for the next seven to ten days. The windy months are December and January, being mostly northerly in direction. The rest of the year is • During the months, October, November, De- between low to mid-speed winds, which are mostly cember and January, the farmers irrigate the in a southerly northerly direction. vegetables for five to six hours between 15:00 and 20:00 hours each four to five days.

4 Mahaad Shammas TRITA LWR PhD Thesis 1031

• During the strong winds the farmers irrigate the The second and third layers are the primary yielding vegetables for five to six hours between 15:00 zones for domestic water supplies, as well as bore- and 20:00 hours every two to three days. holes of the large farms, and occur on the eastern The farmers irrigate during the evenings and night in and western margin of the central freshwater zone as order to reduce the water evaporation losses. The a source for fodder crop irrigation. These large farms farmers usually cut the grass after 45 days, so they cultivate grass as the major crop and the irrigation make between 8-10 grass cuttings annually. The method is drip and spray (Chandler & Al-Abri 1995). farmers in the Awqad area (west Salalah) mentioned Garziz farm is the largest commercial grass farm lo- that they notice that the salinity on their farms is cur- cated in the freshwater zone, with a total cultivated 3 rently (2005) less than it was three to four years pre- area of 360 ha and uses 7.55 Mm /yr. Sahalnawt viously. All the surveyed farms were located south of farm is the second largest commercial grass farm lo- the tube-wells of the re-injection scheme of the cated adjacent to the freshwater zone, with a total 3 treated sewage effluents into the Salalah plain aquifer area of 260 ha and uses about 6 Mm /yr. to halt saline intrusion. This may account for the arti- The main Salalah saturated aquifer layers are the up- ficial recharge by the treated wastewater, since the per Alluvium layer of the Quaternary Age and the operations of injection wells by the reclaimed water second layer of fractured limestone, deposited in the along the coastal zone of the Salalah plain was com- Tertiary Age. The third saturated layer is marly lime- menced in April 2003 and the project is still ongoing. stone, with low transmissivity and porosity. The volume of fresh groundwater in storage in the central Hydrogeology freshwater zone was estimated by D&MI (1991) to be about 340 Mm3 and estimated by Binnie (1999) at The recharge to the aquifer zone in the Adawnib 362.5 Mm3. The Department of Water Resources Formation takes place mainly from Khareef precipi- (DWR) (1999) estimated the aquifer storage at 346 tation in the Jabal (paper 1). This water percolates Mm3. This is the volume of groundwater with salinity through the Umm erRhaduma of the Jabal and flows (EC) <2,000 μS/cm), equivalent to 1,200 mg/l. Bin- out into the plain as subsurface recharge (paper 3). nie (1999) also estimated the volume of brackish Some springs exist along the foot of the Jabal on the groundwater in the eastern brackish zone and in the fault lines. The most notable are Garziz and Sahal- western brackish zone to be about 345.4 Mm3 and nawt springs located in the Salalah plain. The spring 231.8 Mm3, respectively. water flows through a cemented canal and is used to irrigate Garziz and Sahalnawt fodder farms, respectively. GROUNDWATER DEVELOPMENT The aquifer is confined in the Jabal and starts to be- AND MANAGEMENT come semi-confined from the Jabal front and con- Dhofar is the only region in Oman to benefit from a tinues up to the agricultural belt where the ground- substantial amount of rainfall from the southern water is abstracted from wells dug in the Calcarenite monsoon “Khareef”. The Salalah population de- where the aquifer is unconfined (D&MI, 1992). pends entirely on the plain coastal aquifer as the only D&MI (1993) reported that the greatest development natural source of water supply in the Salalah plain. of the high permeability within the Salalah plain aqui- Mechanized well drilling and abstraction was intro- fer occurs in its central part. duced to the Salalah plain in the 1970s. This has cre- The aquifer was modelled using 3 geological satu- ated a pressure on the only water source in the city rated layers. The depth to the water table ranges (Paper 1). Discharge from the aquifer has gradually from 0 m in the coast to 9 m in the north of the cen- increased as a result of the growth in the country tral Salalah plain. The groundwater salinity ranges (Paper 2) and agricultural activity has usually utilized from more than 35,000 ppm in the south to 500 ppm over 70% of the groundwater. in the freshwater zone. The Fars group (Nar & As recorded by the Directorate General of Water Adawnib Formation) generally ranges from 60-70 m, Supply in Salalah City, the potable water increased but thins to the east and west, where it has low per- from 7.8 Mm3 in 1990 to 14.8 Mm3 in 2004. In Sala- meability sediments. The maximum thickness of the lah, where groundwater has been used extensively aquifer is modelled at 70 m. since the mid- 1990s for agricultural, industrial and The upper aquifer layer consists of 20 m thick Qua- municipal purposes, groundwater is withdrawn from ternary Wadi alluvium. This layer is the primary yield- the aquifer more rapidly than it can be replenished by ing zone for the traditional farms in the agricultural natural recharge (Paper 2). The heavy withdrawal of strip and residential vicinity. Those strips have the large quantities of the groundwater from the aquifer majority of the dug wells in the Salalah plain, where leads to the encroachment of seawater (Paper 1). water depth is generally less than 10 m. Boreholes are Previous studies on the Salalah aquifer since the more common on the rest of the plain where water early-1990s, which are mentioned in this study, dem- levels exceed 15 m. The major aquifer layer of the onstrated that the aquifer is facing a challenge in Salalah Plain is the Baleed Member of Adawnib terms of its quality (Paper 1) and quantity (Paper 2), Formation, which is 30 m- 45 m thick. The third which would not be sustainable for future develop- saturated layer is about 20 m thick. ment unless abstraction is controlled (Papers 1 & 2).

5 Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

Natural recharge mated agricultural water demand in terms of net water demand (crop consumption plus evaporation Vertical precipitation losses) was approximately 62 MCM per annum for The Dhofar region receives the monsoon season the 2,819 ha of net-cropped area irrigated. The huge from late June to late September every year. During majority of volume of water used by irrigated agricul- the Southwest monsoon, the mountains of Dhofar ture is not measured (only 4% of agricultural are covered in a dense fog with frequent drizzle and bores/wells have meters (NWI, 1994). light rain with a maximum duration lasting out the The net water demand in the agricultural sector is monsoon. In most years more than 80% of total an- 3 nual precipitation falls during the summer monsoon calculated at 61 Mm /yr (Geo-Resources, 2004). months of June, July and August. Precipitation on Traditionally, the main area of agriculture on the Jabal AlQara occurs as fine mist and rain and occult Salalah plain has been a 2 km coastal zone extending precipitation from fog (Paper 3). The average annual some 20 km from Awqad in the west to Dahariz in rainfall of Jabal AlQara and the Salalah plain is re- the east. These small farms produce a variety of ported in several studies (Paper 3). crops, including coconuts, fruit, vegetables and grass using water from wells dug in the Calcarenite (the Horizontal precipitation upper layer). However, large-scale modern farms Horizontal precipitation is known locally as the inter- have now been developed inland and these use water action between trees and fogwater. The fog moisture from boreholes tapping both the fresh and brackish collection of the Jabal Al Qara has been studied by a water zones. This increase in farming has created a number of Consultants, Ministries and Researchers corresponding increase in water requirements, and a since the end of the 1980s (Paper 3). The inhabitants number of private boreholes have been constructed of the area have known about fog and mist water col- for this purpose. lection in the Dhofar Mountains for many genera- Water resources are utilized for both urban and agri- tions. Only a few decades ago the villages in the cultural consumption. The previous estimation of Dhofar countryside had no access to piped domestic groundwater abstraction for agricultural demand in water networks. Inhabitants harvested water by con- the plain aquifer of the Salalah groundwater basin structing small reservoirs under large trees so they varies from one report to another. Most of the could collect a lot of water during the monsoon sea- wells/boreholes of these farms do not connect to son (Al-Khatheri, 1996). Currently, most of the inflow metres. The exact annual abstraction by agricul- habitants in the Dhofar Mountains have access to a ture, especially from the traditional farms, is not reticulated water supply. known. Chandler & Al-Abri (1995) considered the The numerical study was linked with the field ex- net agricultural demand at 62 Mm3; they also in- periment (Hildebrandt, et al., 2004) in Jabal AlQara cluded the demand from Razat and Sahalnawt farms. (Jojub) between the monsoon of 2003 and 2005. The This work excludes Razat farm and part of Sahalnawt study investigated the relationship between the mon- farm consumption as they are outside the aquifer soon, Jabal vegetations and fogwater interception, model domain of the eastern boundary. So, the net landforms on the recharge of the Salalah plain aqui- agricultural demand is modelled in this study at 46 fer and computed analytically the underflow from Ja- Mm3/yr along the predictive period (Paper 4). bal AlQara to the plain aquifer, to evaluate the aquifer recharge optimized by the steady-state calibrated Groundwater management flow model (Paper 3). What is being done about it? MRMEWR together with MAF are providing the assessment, develop- Discharge from the groundwater ment and management of the water resources in the MRMEWR has initiated a programme of well regis- Dhofar Governate. Furthermore, the government tration and set up a well inventory for the Salalah has implemented several measures to sustain the wa- plain. National Well Inventory (NWI) properties sur- ter resources, which include the facts presented be- veyed the total abstraction rates on the Salalah- low. Taqah plain. According to the NWI (1994), the esti-

a b Fig. 3 Salalah central STP (Raysut area), the aeration tank (a) and the collection tank before discharge (b). Photograph by the author (2004).

6 Mahaad Shammas TRITA LWR PhD Thesis 1031

Monitoring of aquifer performance and protect Salalah City from flooding caused from a DWR has regularly been monitoring the aquifer state temporary tropical cyclone. The cyclonic rainfall will variables of the electrical conductivity and water lev- provide a significant recharge to the system, but it is els since the early 1980s. A database for the EC and not expected to reverse any major increases in salin- water levels of the plain aquifer has also been estab- ity as cyclones occur only on an occasional basis (Pa- lished. The ministry (MRMEWR) integrated a moni- per 1). toring network of rainfall, Wadis, springs gauges as The direct injection of reclaimed wastewater well as wells, wetlands and dams which exceeds 4600 SSDSCo utilises a biological treatment system, monitoring points and covers the most important ar- known as an activated sludge process, to achieve ter- eas of the Sultanate. The staff monitoring water tiary treatment (Fig. 3). The client company expects situations conducts routine monitoring visits, records that the plant will receive 20,000 m3 per day by the the readings and updates the ministry water monitor- year 2007. The processes of the STP in brief are; the ing network database. MRMEWR has a database for preliminary treatment (primary settling basins), the monitoring changes in water levels and electrical secondary treatment (consists of aeration tanks and a conductivity over a large part of the Salalah plain. settling tank) and the final process, disinfection (the This database has allowed the author to develop a used disinfectant is chlorine), which is added before calibrated aquifer model (Papers 1 to 5). The current discharge. The Salalah central sewage treatment plant model should be used, updated and recalibrated as currently receives sewage water of some 18,000 m3 additional data become available to evaluate aquifer per day. performance under a variety of different land uses and management strategies. The STP effluents are treated to the tertiary level. Af- ter the chlorination phase, effluents are discharged Recharge/flood protection dams into a pipeline parallel to the coast and recharged Recharge dams are useful for water resources devel- into tube-wells. The process aims to act as a hydrau- opment. In addition to contributing to increase the lic barrier to combat saltwater intrusion and to partly quantities of water resources and control seawater in- replace water abstracted from hand dug trusion, these dams also act as barriers to control wells/boreholes further inland and downstream (Pa- floods risks. On the Salalah plain, a 22 m high dam per 5). was constructed in 1993 on Wadi Sahalnawt, near the The significance of the injection rates regarding the Jabal front, north of Salalah. Sahalnawt dam has a water balance have increased from 2003 (Fig. 4). 90% capacity of 6.4 Mm3 and has filled one time to date of the treated effluents daily are available for injec- during the tropical cyclone in Dhofar, May 2002. tion, and the balance is currently discharged to Ray- Unpublished data of the DWR recorded that 1.8 sut cement factory and Bir Bint Ahmed farm. The Mm3 flowed over the main spillway of the dam dur- quantities of treated sewage effluents projected in ing the cyclone event at (May 2002). The artificial re- this study, which are available for reuse, is about 6.6, charge of the dam is assumed to be 75% (Al-Battashi 8.6 and 10 MCM for 2006, 2015 and 2020, respec- & Syed 1998; and Atkins, 1989) of the stored vol- tively. These quantities are sufficient to irrigate be- ume, i.e. 6.15 Mm3/yr. tween 273, 356 and 414 Ha, assuming a net water During the last cyclone (May 2002), the existing Sa- demand at 24,170 m3/ha/yr as assumed by Geo- halnawt dam was completely filled and some water Resources (2004). The use of treated wastewater on even overflowed from the top of the dam to the ad- amenity plantings and water conservation measures jacent Sahalnawt Wadi. The mid-part of Salalah was would also be appropriate. flooded and the water was almost half a metre above Reduction of the camel population the ground surface in some areas and in roads and low areas of the city itself. Most of the flooding that The government purchased about forty-five thou- covered the mid-part of Salalah City was from the sand (45,000) camels from the owners in the Dhofar Wadi Garziz flood. D&MI (1992) predicted that a Mountains during 2004 to 2005. The main aim was cyclone would occur in the Dhofar region at a dura- to reduce the camel population, which in turn would tion of once every seven to ten years. In June 1996, preserve the tree canopy in the Jabal. Camel brows- April 1983 and June 1963, major cyclonic storms oc- ing threatens the fog forests in the mountains, espe- curred in the Dhofar Governate. cially those on Jabal crest behind the Salalah plain, that contribute in the plain aquifer recharge (Pa- A design study for two recharge dams at Wadi Garziz per 3). in the central Salalah plain is currently underway with a capacity of 15 Mm3. Only 75% of the stored vol- The number of animals in the Dhofar such as, sheep, ume is assumed to be available as artificial recharge, goats, cattle and camels, were 7,605; 170,123; which means that the existing Sahalnawt dam and 173,892; and 53,527 in 2005, respectively (Oman two more flood control and recharge dams at a ca- livestock census, 2004-2005), whereas in 2002 the pacity of 6.4 and 15 Mm3 would contribute in the re- numbers of goats, cattle and camels were 169,000; charge by 16 Mm3 at times of a cyclone event like the 236,000; and 83,000, respectively. The camel popula- one that happened in May 2002, i.e. equivalent to 2.7 tion has decreased from 83,000 in 2002 to 53,527 in Mm3/yr. The dams will act as an artificial recharge 2005. This accounts for the camel population reduc-

7 Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

Fig. 4 The artificial recharge rates from 12 the Salalah central STP effluents versus time, 2003-2020 10

Volume, M cubic metres 2

0 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Year tion programme that took place in Dhofar between ble the current figures. 2004 and 2005. It is essential to extend the grazing So, is there is any way to bring the recharge to and animals (camels and cows) depopulation project in abstraction from the aquifer into balance? Obviously, the Governate of Dhofar so that livestock owners there is a need to introduce potential management can benefit, while vegetation is used in a sustainable options to carry the aquifer to a balanced state (Ta- manner. Saving the vegetation would enhance the ble 1). This is the main approach of this study. horizontal precipitation and groundwater underflow. It is obvious that the only solutions lie in developing Available measures to government other freshwater sources or reducing freshwater demand. The only potential source of new freshwater is Salalah aquifer receives renewable water through the annual recharge of the aquifer by the Khareef. This through desalination. Demand must be reduced through reallocation of the fixed amount of freshwa- study calculated the current (2005) average annual re- ter available, probably by limiting its use for agricul- charge to the aquifer at about 56 Mm3. However, the tural purposes. Although the majority of the work current average annual abstraction from the aquifer is 65 Mm3. performed by the ENTEC (1998) study was directed towards the qualitative study of the wellfields, they Looking to the future, two things are obvious: stated that the problem of saltwater intrusion is es- • Annual natural recharge to the aquifer will not sentially a quantitative “general” problem that can increase (unless the reduction of the population only be solved by reducing the volume of abstrac- of camels as well as long term tree canopy trans- tion. planting in Jabal Al-Qara are continued and Potential groundwater management solutions to bal- strengthened); and ance the coastal aquifer have been proposed (Pa- • Annual demand for water from the aquifer will per 4). Table (1) shows the suggested management increase. scenarios and their objectives. Predictive scenarios were proposed and assessed using the numerical Thus, the current annual deficit of over 9 Mm3 will simulation model, in order to predict the extent of increase over the coming 15 years to approach dou-

Table 1 Predictive scenario and their objectives Prediction scenarios Objectives Percentage of reduction 1 Relocate Garziz and MAF farms far To see the impact of the relocation The abstraction will be re- from the freshwater zone of the two big grass production duced by 17% farms on the aquifer water balance 2 Suspend the abstraction of the grass To see the effect of this reduction This option will reduce the production for 4 months a year on the aquifer, especially during 4 abstraction by 13% months with high evaporation in Salalah plain 3 Change in irrigation system pattern To see impact of the modern irri- This option will reduce the gation system current abstraction by 20% 4 Establish the Desalination Plant To see the impact of the reduction This will reduce the projected from the potable abstraction from abstraction from 14% to 15% the municipal Wellfields on the between the year 2006 and aquifer balance 2020

8 Mahaad Shammas TRITA LWR PhD Thesis 1031

N S

Fig. 5 The vegetation covers on the Salalah plain and Jabal Al-Qara (from Miller and Morris, 1988) water levels and salinity for the period 2006-2020 tion and restore the plant canopy. Miller & Morris (Paper 4). (1988) mentioned that the ecosystem of the Dhofar region supports more than 750 terrestrial plant spe- Jabal reforestation cies, of which about 50 species are endemic (Fig. 5). Three decades earlier there was an environmental balance between natural resources and grazing activi- The relationship between numbers of livestock and ties within the primary social and economic activity the available grazing areas are unbalanced as a result in Dhofar Mountains. Currently more than half of of continuous grazing pressures on the grasslands. the Dhofar indigenous species are about to become Currently the Jabal is facing severe overgrazing. Al- extinct as a result of overgrazing (personal communi- Khatheri (1996) concluded that animal activities, es- cations with Ahmed Al-Khatheri, MAF-Salalah, pecially overgrazing, had contributed greatly to the March 2006). The population of the grazing livestock deterioration of natural grasslands in the Dhofar (camels, cows and goats) has increased since the mid- Mountains. Natural grassland on the Jabal currently 1970s after the Omani renaissance. The government does not produce its full potential because of the ex- has provided the Jabal inhabitants with needed ser- cessive grazing pressure problem. The importance of vices, i.e. water, by drilling boreholes in the Jabal set- the concept of tree planting in Jabal AlQara for re- tlements. The most significant cause of deterioration forestation and the recharge of the Salalah ground- in the grasslands environment in the Dhofar region is water aquifer through fogwater harvesting has been the increase in the number of animals and the result- stressed in this study (Paper 3). The higher the alti- ing grazing pressure on the grasslands. tudinal range above sea level the higher the potential for fogwater interception in the Dhofar Mountains Jabal reforestation and combating desertification in (Barros & Whitcombe 1989). Dhofar have been investigated by several studies since the early 1980s. Atkins (1989) recommended Irrigation water distribution and efficiency of water use policies for the Jabal reforestation in the regional de- There is a requirement to control agricultural water velopment plan produced for the Dhofar Governate use in the Salalah plain. To put this into effect, MAF on behalf of PCDESR. Travers Morgan (1995) stated would take responsibility for supplying water to that the planting of 2,000 to 4,000 ha of trees on the farms through a main distribution system to individ- Jabal will greatly improve Khareef recharge. Few of ual farms. Water input into the system would be bal- these proposed plans for the Jabal reforestation and anced by having different abstraction rates from dif- anti-desertification in the Dhofar Mountains have ferent wells in the region for the overall benefit of been implemented to date. the aquifer. A metered output, providing a fixed MAF in the 1990s fenced a couple of areas in the Ja- amount of free water in accordance to the farm size, bal to conserve the existing genetics of the indige- would be allocated to each farm. Any water con- nous plants in the Jabal. The government sumed above this amount would be charged for. This (MRMEWR) established a plant nursery in Jabal would encourage farmers to practice efficient irriga- AlQara (Qairoon hairriti- about 872 m amsl) in 2005 tion and allow smallholders to conduct very concise to enhance the conservation of the indigenous plant control over their water. species through transplanting to combat desertifica-

9 Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

Data Collection & Conceptualization

Model Grid Design and Boundary Condition Assignment

Model Data Preparation & Parame- ters Initialization and Input

Calibration by History Matching Under Steady-State and Tran- sient Conditions Numerical Model Construction - Flow - Solute (TDS)

No Is more data needed? Yes

Predictive Simulation Post-Auditing

Fig. 6 The flow chart of the model methodology for flow and solute transport

There are some 1,060 small-scale farmers within Sala- Modern irrigation techniques are in operation in large lah, with holdings ranging from 1 to 5 ha. In these agricultural farms mainly for the production of fod- small-scale farms, the surface methods known as der crops such as alfalfa and Rhodes grass. Modern “flood irrigation systems” are almost exclusively used irrigation has also been promoted on 100 of the tra- and need to be switched over to modern irrigation ditional farms (D&MI 1992). 75% of the project was systems. The efficiency of an unlined flood irrigation funded by MAF whose target was to provide more system is considered the lowest in the order of 50% efficient and productive water use. This project also to 60% against the highest efficiency of 80% included an improvement of the efficiency of water achieved by modern irrigation systems. In drip irriga- used for irrigation in traditional farms to achieve tion, efficiencies are generally 85-90% (D&MI 1992). maximum productivity at the lowest cost, through Trickle irrigation of fruit and vegetable is the most the application of drip or sprinkle irrigation as rec- important new practice required and involves a ommended by MAF. change of farm structure. This measure will reduce Atkins (1989) and Geo-Resources (2004) made a agricultural water use (a 15% saving may be possible) proposal to conserve irrigation supplies to the small- on the plain (Atkins, 1989). Efficiencies can be much scale farmers by the provision of a common water lower due to poor design and management. supply, to be provided from the many existing wells, into a ring main to provide a basic distribution sys-

10 Mahaad Shammas TRITA LWR PhD Thesis 1031

private wells domestic on plain 6% recharge 2% water use TSE 9% 23% underflow agricultural 89% demand 71% Fig. 7 The current (2005) rates of the water resources to the plain aquifer Fig. 8 The current (2005) rate of groundwater utilization from the plain aquifer tem. Farmers would then be allocated a free volume of water every year based on crop and plot size. The MATERIALS AND METHODS application of irrigation water during the night has to The modelling was carried out using a 3-dimensional be encouraged. This will reduce evaporation losses flow groundwater simulation model (McDonald & considerably, especially in the dry season. The proc- Harbaugh, 1988). Solute transport modelling was car- esses of implementing the modern irrigation systems ried out using MT3DMS (Zheng & Wang, 1999), a in Salalah took a long time and it is in the farmer’s mass transport simulation model. The computer hand unless the government applies a tariff on the codes are widely recognized and have been tested water. and verified worldwide. The theoretical basis of the Seawater Desalination Plant model was explained in Paper 4. The key factor in any decision on desalination is the cost and sustainability. The unit cost of desalinated Numerical modelling development water would be approximately 0.660 O.R. (currently The pre-development (no-abstraction flow scenario) equivalent to 1.73 US dollars) per cubic metre, is calibrated by changing the model parameters (hori- (D&MI 1992). A seawater desalination plant option zontal and vertical hydraulic conductivities) inputs in Salalah is now under study. The proposal is based until the water levels of the model become close to on the previous data on the aquifer water budget. the observation water levels in the coastal aquifer. A The desalination plant could cover the water deficit steady-state configuration was developed to repre- in Salalah. Abdel Warith, an engineers’ consultancy, sent the average flow system and to develop the ini- did the study in July 2003 for the office of the Minis- tial conditions for the transient flow model calibra- ter and Governor of Dhofar, D.G. of Water Supply. tions. This study has introduced the methodology of Abdel Warith (2003) has investigated options for dif- proposing and assessing groundwater management ferent plants and power sources. Capital costs for the scenarios to combat saline water intrusion and to first stage construction ranged between M.O.R. 20 to contribute to the sustainable management of 46. The cost of the water supply ranged between groundwater resources in Salalah, using predictive 0.420 and 0.650 O.R/m3. Abdel Warith (2003) pro- simulation and solute transport modelling. The estab- posed a desalination plant for Salalah in three stages. lished flow model is used as a tool to investigate the different management options.

Transient case (1993-2005) Predictive case (2006-2020) 80 Fig. 9 The previous and projected total pumping rates in Salalah plain aq- 70 uifer versus time, 1992-2020 60

Volume, M cubic metres 20

0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

Years

11 Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

The grid size is discretized from (∆x= ∆y) from (320 impacted by over abstraction (Paper 1). DWR (1999) x 320) m at the central of the plain where pumping recommended that a more reliable estimate of re- and injection activities occur, to small values to ex- charge from the Salalah groundwater flow model be amine the grid sizes effect on the model results. The obtained. The recharge would be used as a tool for model shows that the underflow would increase by the effective management of the Salalah plain aquifer. 4% when comparing small grid sizes (32 x 32 m) with This study used a 3-D finite-difference groundwater the large grid sizes (320 x 320 m). Due to the com- flow model to calculate the recharge (Papers 1 & 2). puter memory (RAM) limitations, one uniform grid The total current calculated recharge into the plain size (320 x 320 m) values were used for each layer at aquifer is 56 Mm3, of which 50 Mm3 derives from the central of the plain where pumping and injection the inflow of groundwater coming from the Jabal activities occur. plus the 1 Mm3/yr recharge from plain rainfall; the Within the simulated aquifer domain, 43 observation remainder is from the artificial recharge of treated wells were used. During the calibration process (Pa- sewage effluents. The underflow is the combined re- per 1), the simulation results were checked constantly charge from the vertical component of precipitation against the available observed hydraulic heads and sa- (rainfall/drizzle) and recharge from the horizontal linity levels, and were ended when the results of the component of precipitation (fogwater-mists captured simulated and the observed are obtained. The by Jabal vegetation cover) (Paper 3). calibration procedures and the adopted methodology Currently (2005), the various development sectors in to balance the aquifer were explained in Paper 4. Fig- Salalah depend on the plain aquifer water sources by ure 6 shows the flow diagram of the model method- about 91%, the remaining balance coming from the ology for flow and solute transport. treated sewage effluents supplied by the Salalah central sewage treatment plant in Raysut (Fig. 7). Fogwater Collection experiment The domestic water demand is projected to double in A study was made by Hildebrandt et al. (2004) on the 2020 as a result of the population and tourism and investigation of the hydrology of the Dhofar Moun- industrial growth. The rates of the current groundwa- tain fogwater forest for the MRMEWR and, included ter users of each sector are shown in Figure 8. The an experiment on fog and rainfall collection in Jojub main water consumers of the Salalah aquifer are the locality in Jabal Al-Qara (The author was responsible following sectors: for data collection). The data derived from this ex- • The potable demand; periment, which was collected during the monsoon seasons of 2003, 2004, and 2005, were used in this • The urban/industrial demand; and study, namely the measured parameters of tree stem- • The agricultural use flow and throughfall (Paper 3). The experiment work Currently (2005), the agriculture utilizes about 71% in the Al-Qara Mountain was linked with the theo- of the groundwater. The domestic abstraction is retical study of the flow model to optimize the re- about 23%, of which about 1% is utilized by the in- charge analytically in order to evaluate the output of dustrial sectors in Salalah. Private boreholes use the the recharge obtained by the calibrated flow model. remaining balance of water. Total consumption currently exceeds natural and artificial recharge by 16% RESULTS AND DISCUSSION (i.e., a deficit of 9 MCM) and is expected to increase to exceed the safe yield by 21% in 2020 with a con- Introduction stant underflow (Paper 2). The aim of the study was to determine a number of Simulations were made under an assumption that the options that could be implemented in the region, pumping rates of the domestic water supply from which could be used to provide water services to the Salalah and Saada Wellfields increase according to growing population, as well as reduce the saline in- the population rate and development growth in Sala- trusion on the groundwater resource currently being lah, or about 3% a year. The D&MI (1992) estimated

50 45 Fig. 10 The relationship between the 40 vegetation on Jabal AlQara and the recharge for the Salalah plain aquifer 35 30 25 20 15

Volume, M cubic metres 10 5 0 2005 2006 2007 2008 2009 2010 2011 2012 20132014 2015 2016 2017 2018 2019 2020 Years

12 Mahaad Shammas TRITA LWR PhD Thesis 1031

that the total abstractions from the aquifer will be is predicted to change by 5% annually. The 50 Mm3 82.06 Mm3 in 2020, which is close to the prediction underflow in 2005 is predicted to decrease to 50% in estimation of this study, i.e. that the discharge would 2020 if measures are not implemented to maintain reach 74 Mm3 in 2020. This study’s prediction of the currently available plants on the Jabal AlQara sur- pumping rates is shown in Figure 9. face area (Paper 3). The calculated values of the Garziz & MAF farms and the private production model show that the underflow from Jabal AlQara in boreholes pump from layer two, 10.76 and 4.04 re- 2020 would decrease to less than half of the value de- spectively, equivalent to 23% of the total pumping. rived from the groundwater modelling (23 Mm3 out The potable abstractions from the second and third of 50 Mm3). Hildebrandt & Eltahir (2006) stated that layer of the Salalah and Saada Wellfields are 15.2 the unusual forest could be driven into extinction if Mm3/yr in 2005, equivalent to 23% of total pump- hungry camels continue eating too much of the foli- ing, of which 70% derives from the Salalah Wellfield age. They added, as the greenery disappears, it is pos- boreholes, the remainder from the Saada Wellfield. sible that the trees will lose the ability to pull water from the mist and recharge underground reservoirs. Plain abstractions outside the basin were excluded, e.g. Razat farm, DCFC Sahalnawt farm, which draws The practical experiment of fog collection demon- 6.24 Mm3/yr and 5.68 Mm3/yr, respectively (D&MI, strates the importance of the vegetation in Jabal 1992). Sahalnawt farm abstraction was modelled as AlQara as a source of subsurface recharge by con- being only 4.04 Mm3/yr, since part of the farm bores tributing to horizontal precipitation (Paper 3). As the are outside the aquifer eastern boundary. Jabal AlQara forests act as the surface Salalah aquifer catchment and estimates in this study to provide the This study shows the link between the experimental plain aquifer by between 60% to 80% of its annual work in Jabal AlQara on horizontal precipitation and natural recharge (Paper 3). Some measures have been groundwater recharge, and the groundwater model- taken by the government to sustain the Jabal vegeta- ling of the plain aquifer (Paper 3). The project has tion through the reduction of the population of cam- computed the total annual subsurface inflow from els, which by browsing threaten the fog collecting the Jabal to the coastal aquifer at 53 Mm3/yr, equiva- forest on the Dhofar Mountains. lent to 116 mm/yr, which is higher than the 110 mm/yr that is used from the model groundwater in- Comparative estimation of the recharge is used in flow outputs. Figure (10) shows the potential impor- this project to obtain reliable results of the ground- tant role of plants on Jabal AlQara in the groundwa- water inflow from the adjacent mountains that match ter recharge of the plain aquifer. The change in un- the model inflow outputs. The natural Jabal AlQara derflow is based on the likely deterioration of the subsurface recharge rates are computed at 53 fogwater collection forest on the Jabal behind Salalah Mm3/yr, equivalent to 116 mm/yr (Paper 3). The plain. Figure (10) predicted how the impact of flow model of no-abstraction outputs using large grid browsing increases on the underflow. The underflow sizes (320 x 320 m) calculated the groundwater inflow from Jabal at 50 Mm3/yr, equivalent to 110 Transient case (1993-2005) Predictive case (2006-2020) 110 100 90 80 70 60 50 40 30 20 recharge (baseline A) 10 0 recharge (baseline B) -10 -20 -30 abstraction rates Volume, M cubicmetres -40 -50 -60 -70 -80 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

Years

Fig. 11 The abstraction and recharge rates in Salalah versus time, 1993-2020.

13 Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

a b

Fig. 12 The calculated water levels (m) in Salalah aquifer in 2015 for the baseline scenarios A (a) and B (b) mm/yr (Paper 1), whereas the underflow was the cal- 53% in 2020, under changing underflow. In both culated by the flow model at 52 Mm3/yr, equivalent scenarios, on plain rainfall and annual artificial re- to 114 mm/yr by using small grid sizes (32 x 32 m). charge rates were included through the calibration The result of the recharge evaluation method is too and predictive periods. The irrigation return flows close to the Jabal subsurface inflow of the flow were included in the established model, but excluded model. The evaluation supports the flow model out- during water budget estimations, as the aquifer puts on underflow estimation. freshwater water budget is the concern. Two baseline simulations were run to calculate the This study investigated the effectiveness of artificial piezometric surface and salinity distribution for the recharge in combating seawater intrusion in the Sala- "business as usual" conditions of the aquifer (no- lah coastal aquifer, Oman (Paper 5). The water level management interference). Both scenarios were pre- in some of the observation bores of the injections dicted and simulated from 2006 until 2020. Baseline scheme along the Salalah coastal belt in 2000 and scenarios A, supposes business as usual and the the 2005 shows an increase. This study shows that in the calculated underflow remains constant, domestic Salalah coastal aquifer of Southern Oman, the wedge supply increases by 3% annually and the treated sew- of saline intrusion was delineated, up to 2 km from age system also increases annually at 3%. No- the coast in 2005. The developed flow model pre- management interference scenario A assumes that dicts that the wedge of saline intrusion in 2020 would the efforts to maintain the plant surface area (refores- reach up to 3 and 4 km from the shoreline with the tation) will be implemented (Paper 4). Baseline sce- injection and without the injection, respectively, dur- nario B, assumes business as usual and the underflow ing constant underflow (baseline scenario A). decreases annually by 5%, domestic supply increases Whereas under reducing underflow (baseline scenario 3% annually and the treated sewage system also in- B), the model predicted that the wedge of the saline creases annually at 3%. No-management interference intrusion is tracked up to 9 and 10 km from the scenario B expects no-actions to maintain the forest shoreline with the injection and without the injection, canopy behind Salalah plain or weak efforts that respectively (Paper 5). In the Batinah coastal aquifer could not support the degraded and fragmented eco- of Northern Oman, the wedge of saline intrusion system (Paper 3). The established simulation model was delineated, up to 10 km from the coast (Young et was used to predict the distribution of the piezomet- al., 1998). This study claims that the injection scheme ric surface, salinity distribution, and mass balance is effective in pushing the saline zone front by 700 under these proposed scenarios for the predictive pe- metres in the year 2019. riod 2006-2020. This project assessed the effectiveness of seven scenarios in comparison to the "busi- Piezometric surface ness as usual" conditions (Paper 4). The two baseline scenarios of business as usual illus- No action scenario represents the current situation trate a continuation of the general drop in the poten- without considering the management options. Figure tiometric heads observed in the transient calibration 11 shows the variation of the discharge and recharge and predictive stages (Fig. 12). The model predicted values. The discharge values are higher than the re- an increase in the drawdown by about 30% and 80% charge by 16% in 2005 and are increasing to reach at the end of the prediction period (2020), in com- 21% in 15 years, under constant underflow. The dis- parison to the hydraulic heads in 2006, in baseline charge values are higher than the recharge by about scenario A and B, respectively (Table 2).

14 Mahaad Shammas TRITA LWR PhD Thesis 1031

a b

Fig. 13 The calculated TDS (mg/l) in Salalah aquifer in 2015 for the baseline scenarios A (a) and B (b)

Table 3 The calculated TDS (mg/l) within agricul- Table 2 The calculated drawdown (m) within agri- tural coastal belt (model cell, row 50, column 19) for cultural coastal belt (model cell, row 49, column 19) the baseline scenario A and B for the baseline scenario A and B 2006 2010 2015 2020 2006 2010 2015 2020 Baseline sce- 3,050 3,300 5,550 13,700 Baseline sce- 0.56 0.62 0.67 0.72 nario A nario°A Baseline sce- 3,050 11,420 26,800 30,800 Baseline sce- 0.56 0.66 0.83 1 nario B nario°B Mass balance analysis The declin e in the groundwater levels in the Salalah coast a r e pr edicted by the flow model in the order of Figure (14a) shows the assessment and evaluation of 0.02 and 0.03 m per year in baseline scenario A and the effectiveness of the proposed management op- B, respectively. The drawdown within the agricultural tions for groundwater sustainability by using the coastal belt in baseline B in 2020 is predicted to in- mass balance of the calculated hydraulic heads of ob- crease by 40% more than the drawdown within the servation (E 195200 and 1895000 N). The calculated agricultural coastal belt in baseline A. hydraulic heads under baseline A show that scenario 5 is the best option in terms of its effectiveness to in- Solute transport crease the hydraulic heads in the aquifer through the predictive period. Scenario 4 would be the second ef- The two baseline scenarios of business as usual illus- fective option in terms of maintaining the hydraulic trate a continuation of the general rise in the TDS heads along the predictive period. The calculated hy- observed in the transient calibration and predictive draulic heads under baseline B (Fig. 14b) shows that stages (Fig. 13). Table 3 indicates that the TDS is on scenario 5 is the best option in terms of its effective- the increase through the predictive baseline B sce- ness to increase the hydraulic heads in the aquifer nario however, the model cell, row 50, column 19 is through the predictive period. Scenario 4 would be located about 200 m downward of the treated sewage the second effective option in terms of maintaining injection bore. The TDS of the baseline scenario B the hydraulic heads along the predictive period. within the agricultural coastal belt increases by about four, nine and ten times the 2006 TDS value, for the Figure (15) shows the assessment and evaluation of years 2010, 2015 and 2020, respectively (Table 3). the effectiveness of the proposed management options for groundwater sustainability by using the The saline inflow is reduced by about 70% and 50%, mass balance of the calculated TDS of observation for the scenarios 5, and 6 respectively, compared (AD982274AA). The calculated TDS under baseline with the saline intrusion of baseline B. This may ac- A shows that scenario 6 is the best option in terms of count for the reduction in the underflow, as option its effectiveness to reduce the salinity through the five would limit the abstraction for the domestic de- predictive period. Scenario 2 would be the second ef- mand at 10 Mm3 annually, whereas in the case of fective option in terms of reducing the aquifer salin- changing underflow the domestic demand is on the ity. increase at 3% per year. The model shows that management option 1 would reduce the current abstraction by 17% and scenario 2

15 Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

Transient case (1993-2005) Predictive case (2006-2020) Transient case (1993-2005) Predictive case (2006-2020) 9 b 9 8.5 8.5 8 8 7.5 7.5 7 7 6.5 6.5 6 6 5.5 5.5 5 5 4.5 4.5 4 4 Potentiometric level(m) 3.5 Potentiometric level(m) 3.5 3 3 2.5 2.5 2 2 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Years Years baseline A baseline B sc 1 sc 2 sc 3 baseline A baseline B sc 1 sc 2 sc 3 sc 4 sc 5 sc 6 sc 7 sc 4 sc 5 sc 6 sc 7

Fig. 14 Mass balance of the simulated potentiometric heads for the transient and predictive periods of the two baseline scenarios versus the management scenarios (1993-2020). would reduce the total abstraction by 13%. Manage- ment option 3 would reduce the current abstractions Model limitations by 20%. Scenario 4 would reduce the total abstrac- The southern boundary of the aquifer is at the tion at 14% to 15% for the predictive period. Any of coastal line, some of the model has problems to pro- the suggested management scenarios from 1 to 4 vide the accurate hydraulic heads near the coastline, would not carry the aquifer to balance in the predic- as the south boundary is in direct hydraulic intercon- tive period. There is a need to combine the manage- nection with the saline water. The south boundary ment scenarios together to balance the aquifer in the was set as a fixed head/concentration boundary at next 15 years. Option 5 is introduced as the combi- zero to account for the zero level at the coast. So, ini- nation of 1 and 4, scenario 6 is the combination of 1 tial hydraulic head and concentration at the coast and 3 together, and scenario 7 is the combination of should be specified to avoid model limitations. all options together (1 + 2+ 3+ 4). After the applica- The solute transport model solves the advective tion of the management options, the model shows an transport equations in three dimensions based on increase in the hydraulic heads and a decrease in sa- calculated hydraulic heads and flow terms derived linity levels that varies from one scenario to another. from the groundwater flow model. In this study, a The model shows that best alternative as a long man- solute transport model was established for the aqui- agement term is option 5 but the demand manage- fer using model MT3DMS, and based on the con- ment option 6 seems more environmentally sound. structed transient groundwater flow model In addition, to the link between the experimental (MODFLOW). work in Jabal AlQara on horizontal precipitation and To be able to see the effect of the density in altering groundwater recharge (Paper 3), and the groundwater the flow and salinity evolution patterns, density- modelling of the plain aquifer, the methodology of dependent flow and transport, the density-dependent estimating the underflow, and proposing and assess- flow model is to be used. SEAWAT-2000 software is ing groundwater management scenarios to combat one of the software codes that couples the flow saline water intrusion in the Salalah aquifer using equation in MODFLOW2000 and the transport predictive simulation and solute transport, were the equation in MT3DMS. SEAWAT-2000 is a computer main contribution of this work (Paper 4). programme for the simulation of three-dimensional, The application of a modern irrigation system, such variable-density, transient ground-water flow in po- as in scenarios 3 and 6, will take a long time to im- rous media. plement and remains in the farmers’ hands. There are Despite the above difficulty, this project addresses social and economical challenges from the farmers if the associated limitations and will make refinement the government charges on irrigation. The govern- for future improvements in data availability that ad- ment should compensate the farmers if the irrigation dresses the associated limitations. measures are considered. Declining the underflow concept (Paper 3) is the CONCLUSION AND likely loss of the additional water source from the RECOMMENDATIONS horizontal precipitation, which contributes in the underflow by between 60% and 80% of the total annual underflow, as this ecosystem is under significant Flow model- Conclusions stress from camels feeding on tree canopies. Reduc- Sustainable groundwater management of the Salalah ing grazing animals, such as camels and cattle, as well renewable aquifer requires the demands on the aqui- as the implementation of reforestation programs fer to be in balance with its recharge capacity, in or- would be necessary to maintain the available natural der to maintain the aquifer water quality and water rangelands and underflow to the Salalah aquifer. levels. This study proposes a sustainable management

16 Mahaad Shammas TRITA LWR PhD Thesis 1031

Transient case (1993-2005) Predictive case (2006-2020) Transient case (1993-2005) Predictive case (2006-2020) a 10000 b10000 9000 9000 8000 8000 7000 7000 6000 6000 5000 5000 TDS (mg/l) TDS TDS (mg/l) TDS 4000 4000 3000 3000 2000 2000 1000 1000 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Years Years baseline A baseline B sc 1 sc 2 sc 3 baseline A baseline B sc 1 sc 2 sc 3 sc 4 sc 5 sc 6 sc 7 sc 4 sc 5 sc 6 sc 7 Fig. 15 Mass balance of the simulated TDS (mg/l) for the transient and predictive periods of the two baseline scenarios versus the management scenarios (1993-2020). of groundwater resources in Salalah. In this study, The importance of tree planting in Jabal Al Qara for numerical simulation modelling was used to develop reforestation and the recharge of the Salalah a representative three-dimensional numerical flow groundwater aquifer through fogwater harvesting has and solute transport model for the Salalah coastal been stressed in this study. aquifer using computer codes MODFLOW and The current (2005) water consumption is 16% higher MT3DMS. than the resources currently available from renewable The constructed model was used to predict, under and treated wastewater. In 2020, this will reach 21% transient conditions, the future behaviour of the aq- more than the safe groundwater yield with no- uifer under proposed demand management- management interference under constant recharge. conservation and supply augmentation programmes Thus, the groundwater in Salalah catchments is ex- for the period 2006-2020. Two baseline scenarios tensively declining. were run to calculate the potentiometric surface and The effectiveness of the drawdown in baseline sce- salinity distribution for the "business as usual" condi- nario B "business as usual" under changing under- tions of the aquifer (no management interference). flow by 5% annually was more pronounced than the Both "business as usual" baseline scenarios show the baseline scenario A "business as usual" with constant expected aquifer hydraulic heads and salinity distribu- underflow through the predictive period. tion with no-management interference for the com- The proposed management scenarios show the posi- ing 15 years. tive effect on the aquifer water qualities and quanti- The project shows the link between the experimental ties. Option 1 would reduce the current discharge by work in Jabal Al Qara on horizontal precipitation and 17% and option 2 would reduce the current dis- groundwater recharge, and the groundwater model- charge by 13%. Option 3 would reduce the current ling of the plain aquifer. The flow model calculates discharge by 20% and option 4 would reduce the aq- the groundwater inflow from Jabal Al Qara at 50 uifer discharge by 14% - 15%. Any of the four op- Mm3/yr. The underflow estimation derived from the tions (1-4) would not carry the aquifer to balance in experimental work on Jabal Al Qara is 53 Mm3/yr. the next 15 years. So, the underflow from Jabal Al Qara to the Salalah Two other options were proposed to balance the aq- plain aquifer is between 50 Mm3/yr to 53 Mm3/yr. uifer. Option 5 would decrease the discharge by The practical experiment of fog collection demon- about 31% and option 6 would decrease the dis- strates the importance of the vegetation on Jabal charge by 26%. Options 5 or 6 would secure the aq- AlQara as a source of subsurface recharge by con- uifer water budget for the coming 15 years. tributing in horizontal precipitation. The relocation of Garziz and MAF farms as well as About 98% of the total natural recharge amount changes in irrigation system patterns would provide originates from the adjacent Jabal Al Qara, and the the best scope for managing the aquifer system, and balance from the direct precipitation on the coastal prevent the inland aquifer from further encroach- plain. There is a direct relation between the health of ment. the woodlands and grassland and the efficiency of The injection scheme of the treated wastewater in the water recharge to the Salalah plain, during the mon- Salalah plain aquifer has helped to stabilize the water soon from water collected from mist and fog in the levels. The injection scheme would be less effective Jabal. This study urges that the horizontal precipita- with no-management interference, particularly in the tion caused by fogwater capture by Jabal vegetation, eastern and western parts of the coastal areas as the contributes in the annual natural recharge by 60% to underflow flushing is weak in comparison to the 80%. flushing of the underflow in the central part of the Salalah plain.

17 Sustainable management of the Salalah coastal aquifer in Oman using and integrated approach

The flow model demonstrated that high drawdowns audit of all residential, commercial, govern- are unusual in a highly transmissive karstic aquifer ment/institutional/industrial boreholes/wells is un- with a direct dynamic connection to the sea, such as dertaken. the case of the Salalah coastal aquifer, because unlim- In the future, regarding the study of groundwater ited inflows from the sea rapidly compensate for any management systems by artificial recharge, it is rec- depletion in freshwater storage. ommended that an evaluation be made after five years of operation. Solute transport model– Conclusions Groundwater modellers' scientists recommend a pre- The effectiveness of salinity intrusion in baseline diction time length to be the same as the calibration scenario B "business as usual" under changing under- time length. flow by 5% annually is more pronounced than the The government (MAF) should monitor the system baseline scenario A "business as usual" with constant by placing flow meters in each farm well, in order to underflow through the predictive period. The TDS know the water quantity that each well is pumping. within the agricultural coastal belt in baseline B in Furthermore, a regulation of this matter must be is- 2020 is predicted at more than twice the TDS within sued to enable the authorities to take actions and any the agricultural coastal belt in baseline A and more amounts above the free allocation would be subject than 12 times the current (2005) TDS within the ag- to a penalty charge. ricultural coastal belt. To combat desertification, the government should The annual average predicted increase in the continue supporting the effort exerted to control groundwater salinity in the Salalah coast is at about overgrazing in the Jabal area of the Dhofar Gover- 12% in baseline scenario A, for the years 2006 to norate, so that the vegetation cover could assist in 2020. Whereas in baseline B, the annual average pre- recharging the underground reserves to support the dicted increase in the groundwater salinity in the water position at the Salalah plain. Salalah coast is at about 20%, for the years 2006 through 2020. In baseline scenario B, the salinity will These policies are required to protect the groundwa- increase sharply and that accounts for the change in ter of the Jabal as it contributes towards 98% of the the underflow in the scenario. recharge. A policy to combat desertification in the Dhofar region is very essential to protect what re- It is predicted that by the year 2020 the aquifer water mains of the Jabal’s unique biodiversity and to en- levels would decline under constant recharge by hance the groundwater recharge to the Salalah aqui- about 216% within the Salalah Wellfield location, fer. from their levels in 2006 and would cause a reversal of flow from the sea, and the freshwater/seawater It is essential to extend the grazing animals (camels front will move by 3 km inland with the injection. and cows) depopulation project in Jabal Dhofar, so This would make large areas of the aquifer unusable. that livestock owners can benefit while vegetation is used in a sustainable manner. Reducing grazing ani- This study argues that the injection scheme is effec- mals, such as camels and cattle, as well as the applica- tive in pushing the saline zone front by 700 metres in tion of reforestation programmes, would be essential 2019. The injection scheme of the treated wastewater to sustain the available natural rangelands. helps to reduce the influence of saline inflows from the coast. This study emphasizes the importance of implementing a major programme of enhancing fogwater col- Under constant underflow, option 6 seems the best lection. Tree planting in the grassland is proposed management scenario in terms of reducing the TDS, with the principle purpose of causing an increase in whereas under changing underflow option 5 seems fogwater interception to benefit grassland production the best management scenario in terms of reducing and cause increased groundwater recharge. the TDS. Evaluation of suitable recharge methods and predic- Recommendations tions about further effects using both groundwater and hydrogeochemical modelling are to be consid- Unless aquifer exploitation is decreased, the original ered. objectives of using artificial recharge to store fresh water cannot be met in the long run. This project More research on the links between climate and wa- stresses the importance of achieving a rapid reduc- ter resources in the region must be undertaken. tion in current aquifer over abstractions to ensure the Moreover, increased public awareness of water re- aquifer sustainability. This project recommended the source issues in the region, especially to the owners relocation of Garziz and MAF grass farms of low of the farms, must be initiated. crop value, along with a change of the irrigation sys- MT3DMS is a solute transport model, and as density- tem patterns. Furthermore, other costly measures, dependent factors are of concern, it is important to such as the establishment of a desalination seawater utilise density-dependent flow and transport software plant in Salalah plain, are examined. codes, such as SEAWAT-2000, SUTRA etc, in future In order to obtain a more accurate understanding studies in the Salalah aquifer. and to enable the management of water abstraction from the freshwater lens, it is recommended that an

18 Mahaad Shammas TRITA LWR PhD Thesis 1031

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