Teesta River Agreement between India & Bangladesh: Why Controversy?

As such an old topic but came in news against because Modi's Bangladesh visit.
Geography of Teesta River:
Teesta originates from Kangse Glacier, Charamu Lake in Sikkim, most of its catchment area lies in India. It enters Bangladesh, joins Brahmaputra, and ends in Bay of Bengal.After Brahmapurta, Ganges and Meghna also joins it; Teesta is the 4th largest river in Bangladesh.
Sequence of events:
-W.Bengal government began constructing a barrage and catchment area on Teesta.
-Bangladesh opposed, because their “rice bowl” Rangpur region depends on Teesta.
-To pacify them, India began negotiation.
1983: India- Bangladesh concluded and ad-hoc agreement on Teesta. Who gets how much?
Water share from Teesta..
India 39%
Bangladesh 36%
Unallocated 25%
But problem unsolved, because Bangladesh wanted equal sharing.
1984: Joint-river commission appointed to collect hydrological data & suggest a rational method for water sharing. Commission recommended increasing
Bangladesh’s share, on logic that W.Bengal’s barrage is very close to Bangladesh border (~90 km). Some water will penetrate underground and benefit both countries anyways.
New formula proposed
Water share from Teesta
India 42.5%
Bangladesh 37.5%
Unallocated 20% for the river (otherwise nothing will reach to Bay of Bengal!)
2010:
Bangladesh Teesta Water sharing & Terrorism 
BANGLADESH: TEESTA WATER SHARING TO TERRORISM
Jamaat-ud-Dawah (JuD) calls Pakistani political establishment to stop Indians from constructing dams on rivers flowing to Pakistan, raise the matter in UN, asked civil society(!) to support this cause. And even suggested that Kashmiri Mujahideen should be given a “Free hand” to destroy Bhakra dam!
In other words, Hafiz Saeed is using “economy/farmers’ plight” as a new propaganda tool to promote terrorism.
Sep. 2011
Mohan plans to visit Bangladesh, sign accords for Teesta and Land border disputes.
He invited five state CM that share border with Bangladesh, to join him in this visit.
But on eleventh hour, W.Bengal CM Mamata
Banerjee dropped from this visit to protest against Teesta sharing agreement.
W.Bengal CM Mamatha’s position:
This treaty will dry out Northern region of W.Bengal & hurt Indian farmers.
1998: Bangladesh’s largest irrigation project
“Teesta Barrage” began. With help of this water, Bangladeshi farmers already have three cropping seasons per year. So, they don’t deserve any more water. At that time, Trinmool Congress was the single largest coalition partner in UPA, therefore Mohan had to drop the Teesta accord. He could only sign Land boundary agreement with Bangladesh.
^Ok this is upto 2011. why is the topic in news in 2014?
March 2014
BIMSTEC summit held at Nay Pyi Taw in Myanmar. Mohan assured Haseena about early conclusion of Teesta accord.
April 2014
On Indian side On Bangladeshi side Mamatha tells voters to “teach a lesson” to Congies.
Because otherwise next Congi PM will sign
Teesta accord = Northern parts of W.Bengal will become dry, water shortage for drinking and irrigation. Terrorist Parties like Jamaat-e-Islami & their supporters like Khalida Zia have started Dharna pradarshan in Dhaka’s Jantar Mantar.
Their claim “India has reduced releasing water from Teesta but Hasina’s “Secular” Bangladesh Awami League party is doing nothing to get fair share from Teesta. Bangladeshi paddy farmers are suffering!” (Recall the same propaganda by Jamaat-ud-Dawah (JuD) in Pakistan in 2010.
May 2014
Bangladesh PM Hasina says “India’s central government (Mohan) was sincere, but Mamata raised objections hence the deal could not be.signed.”
June 2015
Teesta takes back seat as land deal grabs spotlight. No serious efforts to resolve the case.

Source: Praful Bhardwaj from Team work for CSE-2015