Büyük Cırcıp Yeraltısuyu Besleme Brajının HYDRUS-1D ile Modellenmesi

Öz

Bu çalışmada, Büyük Cırcıp Yeraltısuyu Barajından yeraltı suyuna sızan su miktarı ve sızma süresi Hydrus-1D sayısal modeli kullanarak belirlenmiştir. Fırat nehri üzerinde bulunan Büyük Cırcıp yeraltısuyu besleme barajı Güneydoğu Anadolu Projesinin (GAP) bir parçasıdır. Yıllık yağış miktarının yüksek olduğu Ekim-Mayıs arası dönemde toplanan taşkın suları 1.75 hm3’tür. Sızmanın z-yönüne dik tek boyutlu olduğu göz önüne alınarak,1 boyutlu infiltrasyonu modellemek üzere bu duruma uygun olarak Hydrus-1D modeli kullanılmıştır. 1 Boyutlu Hydrus sayısal modeli su akımı ve farklı doygunluktaki ortamlarda madde taşınımı modellenmesinde kullanılan en yaygın modellerdendir. Bu model Richards denklemini sonlu elemanlar metodunu kullanarak çözümlemektedir. Bu çalışmada yeraltı suyu debi miktarı ve infiltrasyon süresi 1) 100 yıllık taşkın ve 2) Yıllık yağış miktarları göz önüne alınarak hesaplanmıştır. Çalışmadan elde edilen sonuçların yorumlanması ile, baraj gölünün tabanından sızmayı artırmak için daha az hidrolik geçirgenliğe sahip 15 m kalınlığındaki alüvyon tabakada açılan kuyularla suyun yeraltısuyuna doğru infiltrasyonu artırılmıştır. Yıllık yağış potansiyeli göz önüne alındığında baraj gölünden yıllık yeraltı suyuna deşarj 97 hm3’tür. Bu çalışmada, GAP kapsamında yapılması planlanmış 13 barajdan biri olan Büyük Cırcıp baraj gölünden yeraltı suyuna sızdırılan su miktarı yıllık 10 hm3 olarak bulunmuştur.

Anahtar Kelimeler

• Yeraltısuyu Besleme,Güneydoğu Anadolu,Tekrar Şarj

Modeling of Büyük Cırcıp Groundwater Recharge Dam using HYDRUS-1D

Abstract

The purpose of this research is estimation of duration and amount of infiltration from the dam reservoir of Büyük Cırcıp groundwater recharge dam by Hydrus-1D model. Büyük Cırcıp groundwater recharge dam is one of the element of the southeastern Anatolian project in Turkey located on one of minor watercourse of great Euphrates River. The collected flood waters from rainy season (from October to May) are controlled by this small dam with 1.75 hm3 storage volume. The recharge dam reservoir bed has 15 meters thick alluvium layer overlain a permeable limestone. Groundwater depth under the reservoir is about 55 meters. The water seepage in this groundwater recharge dam is considered mainly vertical in the z-direction, therefore HYDRUS-1D software is suitable for modeling such 1-D infiltration. HYDRUS-1D, one of the most widely used models, can model water flow and solutes transport through the variable saturation media. The model uses finite element method for solving the Richards flow equation and contaminant transport equation. In this study, the model was used to calculate amount and duration of infiltration effectively under two cases: 1) 100-years flood and 2) annual flow. Results show that the time to fill up the dam depends on the hydrograph characteristics while the time to empty is related to the hydrogeological character of the reservoir bed alluvium. A sensitivity analysis for hydraulic conductivity of the alluvium was performed using the model. According to the results, technical recommendations were suggested to improve the efficiency by implementing a group of recharge wells to accelerate water infiltration through 15-m thick alluvium layer under the reservoir that has low permeability. The annual potential groundwater recharge for the basin was reported 97 hm3/year, however, this study shows that the infiltrated water into the ground through Büyük Cırcıp dam is about 10 hm3/year, which is one of 13 dam projects are planned to be implemented by GAP.

Keywords

• groundwater,recharge,hydrus,Southeastern Anatolia

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